| Physics at the University of Virginia | ||||||
| Academics | People | Research | Announcements | Facilities | Administration | Classes |
| Friday, October 29, 1999 | Alwyn Wootten [Host: Bascom Deaver] | |
| 4:00 PM, Room 204 | National Radio Astronomy Observatory | |
| Physics Building | “The Atacama Large Millimeter Array: Imaging Cosmic Dawns” |
| The Atacama Large Millimeter Array (ALMA), a project of the National Radio Astronomy Observatory and the European Southern Observatory, will be built over the coming decade in Northern Chile. ALMA will be a revolutionary telescope, operating at millimeter and submillimeter wavelengths and comprised of an array of individual antennas each 12 meters in diameter that work together to make precision images of astronomical objects. The goal of the ALMA Project is an array of 64 antennas that can be positioned as needed over an area 10 kilometers in diameter so as to give the array a zoom-lens capability. ALMA will image the universe with unprecedented sensitivity and sharpness at millimeter and submillimeter wavelengths. The energy density of radiation from both the Milky Way and from the diffuse extragalactic background peaks in the submillimeter. Aside from Cosmic Microwave Background photons, submillimeter photons are the most abundant photons in the Universe. Detailed imaging at these wavelengths will be a major step for astronomy, making it possible to study the origins of galaxies, stars and planets. |
| Friday, November 5, 1999 | David Spergel [Host: Peter Arnold] | |
| 4:00 PM, Room 204 | Princeton University | |
| Physics Building | “Cosmic Microwave Background Fluctuations: A Probe of Cosmology” |
| Observations of the microwave background are a powerful probe of the physics of the early universe and of cosmological parameters. Over the past few years, there has been a dramatic improvement in the quality of data. The current observations are consistent with a flat universe with a cosmological constant in which inflation produced the primordial fluctuations. Next year, NASA plans to launch MAP, a satellite that will make precision measurements of microwave background fluctuations. With these measurements, we will be able to test our basic cosmological paradigm. If correct, we can then use these observations to measure the basic cosmological parameters to high precision. |
| Friday, November 12, 1999 | Professor Ctirad Uher [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | University of Michigan | |
| Physics Building | “Materials with Open Structures as Novel Thermoelectrics” |
| Friday, November 19, 1999 | Jim Stone [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | Boston University/Department of Energy | |
| Physics Building | “Neutrino Mass--Experimental Results from Super-Kamiokande” |
| Friday, December 3, 1999 | Prof. Sid Redner [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | Boston University | |
| Physics Building | “Aggregation Kinetics in Gelation, Traffic, Wealth, and other Everyday Phenomena” |
| In aggregation, clusters meet and irreversibly merge so that their average size grows continuously with time. This process describes, for example, making of jello and yogurt, raindrop formation in clouds, and the mass distribution of stars. I will present an elementary overview of cluster evolution in such aggregating systems. I begin by outlining the mean-field theory of aggregation and showing how scaling provides basic insights into long-time behavior. I will then discuss the intriguing relation between the cluster-size distribution and the first-passage probability of a random walk. Finally, I will discuss recent applications to traffic clustering and the distribution of wealth. |
| Friday, January 28, 2000 | Robert Hull [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | Dept. Materials Science and Engineering, UVA | |
| Physics Building | “New Techniques For Nanoscale Fabrication And Characterization” |
| The gallium focused ion beam produces highly collimated (10 nm - 1(mu)m) beams of high energy (3 - 30 kV) ions. These beams may be used as nanoscale “scalpels” to micromachine virtually any material by direct sputtering of the target surface. Combined with ion-beam induced deposition from organic vapors, this provides unique capabilities for sub 100 nm fabrication of three dimensional structures. I will describe how these capabilities form the basis of a new “nanoprinting” technology, for deep sub-micron pattern definition over planar and curved surfaces. In addition, imaging and spectroscopy in the focused ion beam system enables new routes for three-dimensional characterization and visualization of microscale structures. During sputtering by the primary beam, large numbers of secondary electrons and ions are produced, which may be used to form images of the sputtered surface. By concatenating images of surfaces at different depths during the sputtering process, three-dimensional reconstructions of the structure may be generated. These reconstructions can contain up to 107 independent pixels of information. Furthermore, using a quadrupole mass spectrometer, element-specific images may be obtained. These techniques enable “miroscopy in the third dimension” which can be of immediate and powerful impact in understanding material microstructure. |
| Friday, February 4, 2000 | Eugene Kolomeisky [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Breaking a one-dimensional chain: fracture in 1 + 1 dimensions” |
| The breaking rate of an atomic chain stretched at zero temperature by a constant force can be calculated in a quasiclassical approximation by finding the localized solutions ("bounces") of the equations of classical dynamics in imaginary time. We show that this theory is related to the critical cracks of stressed solids, because the world lines of the atoms in the chain form a two-dimensional crystal, and the bounce is a crack configuration in (unstable) mechanical equilibrium. Thus the tunneling time, Action, and the breaking rate in the limit of small forces are determined by the classical results of Griffith. For the limit of large forces we give an exact bounce solution that describes the quantum fracture and classical crack close to the limit of mechanical stability. This limit can be viewed as a critical phenomenon for which we establish a Levanyuk-Ginzburg criterion of weakness of fluctuations, and propose a scaling argument for the critical regime. The post-tunneling dynamics is understood by the analytic continuation of the bounce solutions to real time. |
| Friday, February 18, 2000 | Paul Fendley [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | Univerisy of Virginia - Physics | |
| Physics Building | “The Observation of Fractional Charge” |
| Friday, February 25, 2000 | Takeshi Egami [Host: Despina Louca] | |
| 4:00 PM, Room 204 | University of Pennsylvania | |
| Physics Building | “Dealing with Regional Conflict: Spin-Charge Inhomogeneity in Superconducting Cuprates and CMR Manganites.” |
| The discovery of high-temperature superconductivity was a double shock to the condensed matter physics community. Not only the critical temperature was so outrageously high (until then 30 K was considered to be the theoretical maximum), but magnetism appeared to be intimately involved, while for a long time magnetism had been considered to be incompatible with superconductivity. It then became the holy grail of theoreticians to overcome this apparent paradox, and various high-wire-act theories have been proposed. In the meantime, experimental data are accumulating that suggest a more conventional method of avoiding regional conflict between the spin and charge, by segregation. However, just as the social and international problems complete segregation simply defers the problem and does not solve it. Oxides are far ahead of us, and appear to have reached an intelligent solution. We discuss the results of recent inelastic and elastic neutron scattering measurements on cuprates and manganites, and speculate what this solution might be. |
| Friday, March 3, 2000 | Roger Chevalier [Host: P. Q. Hung] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Supernova - Gamma Ray Burst Connection” |
| Friday, March 10, 2000 | Eric Zimmerman [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Columbia University | |
| Physics Building | “Searching for new particles in a high-energy neutrino beam: New results from Fermilab” |
| Friday, March 17, 2000 | Prof. Gerassimos (Makis) Petratos [Host: Oscar Rondon] | |
| 4:00 PM, Room 204 | Kent State University | |
| Physics Building | “Elastic Electron Deuteron Scattering: Past, Present and Future” |
| This talk will present a review of elastic electron scattering off the simplest nucleus, the deuteron. The elastic scattering process has long been a crucial tool in understanding the internal structure and dynamics of the nuclear two-body system. Studies of the deuteron form factors, measured in elastic scattering, offer unique opportunities to test both the conventional meson-nucleon "standard model" that describes the deuteron electromagnetic structure, and "nuclear chromodynamics" predictions of perturbative Quantum Chromodynamics based on the underlying quark-gluon substructure of the deuteron. A review of both the theoretical framework and of past (SLAC) and recent (JLab) measurements of the deuteron form factors will be presented |
| Friday, March 24, 2000 | Yongsheng Gao [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Harvard University | |
| Physics Building | “On the road to measure CP violation and test the Standard Model:Observation of hadronic b --> u transitions” |
| CP violation is one of the great mystery of the universe. The major motivation of the first-generation B factories is to measure CP violations in the B meson system, especially the three CKM angles Alpha, Beta and Gamma. I'll present the first observation of hadronic b --> u transitions (B --> Pi+Rho-, Pi+Rho0, Pi+Pi-) which will be very important for the future measurements of the CKM angles Alpha and Gamma. Measuring Alpha and Gamma using these decay modes at the first-generation B factories will be discussed, along with a future outlook of B physics |
| Friday, March 31, 2000 | E. Fischbach [Host: Rogers Ritter] | |
| 4:00 PM, Room 204 | Purdue University | |
| Physics Building | “The Search for Non-Newtonian Gravity” |
| Ongoing attempts to unify the known fundamental forces lead to the suggestion that there may exist new gravity-like forces in nature. These would arise from the exchange of new light bosonic quanta among the constituents of ordinary matter, and would produce apparent deviations from the predictions of Newtonian gravity. The suggestion of such a "fifth force" in 1986 has led to a broadened view of the interaction of gravity and other known and hypothetical forces, and has helped to stimulate a large number of new experiments to search for weak long-range forces. This talk will review both the theoretical motivation for such new forces, and the experimental results that have been obtained to date. More recently newer string-inspired theories have suggested the presence of additional macroscopic forces acting over sub-millimeter distances. Detecting such forces presents special challenges-both theoretical and experimental- for reasons that I will discuss. |
| Friday, April 14, 2000 | Eugene Kolomeisky [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Superfluidity in low dimensions: beyond the mean-field theory” |
| The Gross-Pitaevskii approximation is a long-wavelength theory widely used to describe a variety of properties of dilute Bose condensates, in particular trapped alkali gases. In this talk I will show that for short-ranged repulsive interactions this theory fails in one and two spatial dimensions, and appropriate low-dimensional modifications will be proposed. The new theory has a universal character, and some of its implications such as density profiles in confining potentials, superfluidity, solitons, and self-similar solutions will be discussed. |
| Friday, April 28, 2000 | Joel Fajans [Host: J. Dorning/Joseph Poon] | |
| 4:00 PM, Room 204 | University of California at Berkely | |
| Physics Building | “Pure-Electron Plasma Experiments” |
|
Plasmas made only of electrons are remarkably stable and manipulatable. They are ideal for studying basic plasma physics, two-dimensional fluid dynamics, and nonlinear dynamics. I will discuss some basic plasma results, including a demonstration that like charges can attract rather than repel, and that sometimes mountaintops are just as stable as valley floors. Next I will describe some fluid results like the instability shown in the figure below. Finally I will discuss autoresonance, a very basic and general phenomenon which occurs in nonlinear oscillator systems.
|
| Friday, September 1, 2000 | Shaul Mukamel [Host: Ian Harrison] | |
| 4:00 PM, Room 304 | University of Rochester - Chemistry Dept. | |
| Chemistry Building | “Collective excitations and Multidimensional optical spectroscopies of dendrimers and biomolecules” |
| Friday, September 15, 2000 | Professor Subir Sachdev [Host: Eugene Kolomeisky] | |
| 4:00 PM, Room 204 | Yale University | |
| Physics Building | “ Quantum criticality in the high temperature superconductors” |
| I discuss the phases and critical points of quantum antiferromagnets in two dimensions and their relationship to the physical properties of the high temperature superconductors. Non-magnetic impurities are argued to be a sensitive probe of the wavefunction of the electron spins: I will describe recent experiments on such impurities and the theoretical insights they have provided on the interplay of antiferromagnetism and superconductivity. |
| Friday, September 22, 2000 | Laszlo Tisza [Host: Vittorio Celli] | |
| 4:00 PM, Room 204 | MIT | |
| Physics Building | “History of the two-fluid model and Bose-Einstein condensation” |
| Friday, September 29, 2000 | Richard Hughes [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | Los Alamos National Laboratories | |
| Physics Building | “Quantum cryptography” |
| Quantum cryptography, or more accurately quantum key distribution (QKD), uses single-photon transmissions to generate the shared, secret random number sequences, known as cryptographic keys, which are used to encrypt secret communications. Appealing features of QKD are that its security is based on principles of quantum physics and attempted eavesdropping can be detected. (Heisenberg’s uncertainty principle ensures that an adversary can neither successfully tap the key transmissions, nor evade detection because eavesdropping raises the key error rate above a threshold value). I shall describe two quantum cryptography systems, based on the transmission of non-orthogonal single-photon states to generate shared key material, at Los Alamos. In one experiment we are generating key material over a 48-kilometer optical fiber path, and in the other by transmitting photons over a 1.6-km atmospheric path in daylight. In both cases, key material is built up using the transmission of a single-photon per bit of an initial secret random sequence. A quantum-mechanically random subset of this sequence is identified, becoming the key material after a data reconciliation stage with the sender. The atmospheric results show that QKD could be used for surface to satellite transmissions. |
|
Monday, October 2, 2000 Note Special Day |
Max Tegmark [Host: T. X. Thuan] | |
| 4:00 PM, Room 201 | University of Pennsylvania - Physics Dept. | |
| Astronomy Building | “Zeroing in on cosmological parameters” |
| I describe the sharp constraints on cosmological paramaters placed by recent measurements of the cosmic microwave background, distant supernovae, galaxy clustering, etc., and how different types of measurements how allow powerful cross-checks to be made. I also comment on outstanding puzzles in the emerging cosmological "standard model" and upcoming measurements that may resolve them. |
| Friday, October 6, 2000 | Professor Marvin Girardeau [Host: Eugene Kolomeisky] | |
| 4:00 PM, Room 204 | University of Arizona | |
| Physics Building | “Theory of de Broglie Waveguides” |
| Several experimental groups have recently succeeded in constructing quasi-one-dimensional (1D) atom waveguides and loading them with Bose-Einstein condensates of ultracold atomic vapors. An important motivation for such studies is the goal of constructing atomic de Broglie wave beam splitters and interferometers for ultrasensitive detection of very weak accelerations and gravitational perturbations. This talk will discuss the many-body Schrodinger dynamics of 1D systems of impenetrable bosons, which is exactly soluble via an exact mapping from an ideal Fermi gas to a strongly interacting Bose gas of impenetrable point particles. After description of some completed work on such systems in 1D toroidal geometries and harmonic traps, some work in progress will be described, concerned with a generalization to a model of a de Broglie beam splitter/interferometer using two coupled waveguides. |
| Friday, October 20, 2000 | Joe Thompson [Host: Shivaram] | |
| 4:00 PM, Room 204 | LANL | |
| Physics Building | “Superconductivity in a New Family of Heavy-Fermion Compounds” |
| The discovery of superconductivity in CeCu2Si2 nearly 20 years ago was totally unexpected and contradicted fundamental tenants of the well-established BCS theory of superconductivity. Instead of the magnetic moment carried by Ce+3 suppressing superconductivity, as expected from BCS, the presence of Ce was essential for superconductivity and responsible for increasing the effective mass of the electrons participating in superconductivity by orders-of-magnitude-hence, heavy-fermion superconductivity. As we now know, CeCu2Si2 was the first example of superconductivity mediated by antiferromagnetic spin fluctuations, which also may be the dominant pairing mechanism in high-temperature superconductors, and other parallels between heavy-fermion and cuprate superconductivity are emerging. Recently, we have discovered a new family of heavy-fermion materials, CeMInsub5 (M=Rh, Co, and Ir), in which superconductivity appears at temperatures higher than in any other heavy-fermion system. These materials form in a quasi-2D structure, which makes an analogy with the cuprate's magnetism and superconductivity appealing. Though much remains to be learned about their properties, this new family appears to be quite interesting and provocative. |
| Friday, October 27, 2000 | Boris Kayser [Host: P.Q. Hung] | |
| 4:00 PM, Room 204 | National Science Foundation | |
| Physics Building | “ Why do We Think Neutrinos Have Mass? And What's Next? ” |
| We explain why the evidence for nonzero neutrino masses is compelling. Then, we turn to the questions about neutrinos raised by the presence of their nonzero masses. These questions include: How many different neutrinos are there? How much do they weigh? Is each neutrino identical to its antiparticle? How will we answer questions like these? |
|
Wednesday, November 1, 2000 Note Special Day |
Yanhua Shih [Host: O. Pfister] | |
| 4:00 PM, Room 204 | Univ. of Maryland Baltimore County | |
| Physics Building | “Quantum Entanglement and Quantum Teleportation” |
| Friday, November 3, 2000 | Margaret Murray [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | Department of Mathematics, Virginia Tech | |
| Physics Building | “Women Becoming Mathematicians: The Doctoral Classes of 1940-1959” |
| I give a report on an oral history-based study of the approximately 200 women who earned Ph.D.'s in mathematics from American colleges and universities during the years 1940-1959. I focus in some detail on the following questions: How did the women of this generation develop their mathematical interests and ambitions? Which individuals and institutions were particularly supportive of their mathematical goals? What obstacles to professional success did they encounter as they tried to build careers in mathematics? How did they balance the competing demands of career and personal life? How did they strike a balance between teaching, research, and service to the profession? What lessons can contemporary mathematicians, male and female, learn from the experiences of this generation? |
| Friday, November 10, 2000 | Rick Trebino [Host: Louis Bloomfield] | |
| 4:00 PM, Room 204 | Georgia Tech | |
| Physics Building | “The Musical Score, the Fundamental Theorem of Algebra, and the Measurement” |
| To measure an event in time requires a shorter one. As a result, the development of a technique to measure ultrashort laser pulses--less than 10-12 seconds long and the shortest events ever created--has been particularly difficult. We have, however, recently developed a simple method for fully characterizing these events, that is, for measuring a pulse's intensity and phase vs. time. This method relies on two seemingly unrelated ideas: the concept of the musical score and the fact that the Fundamental Theorem of Algebra fails in two dimensions. Specifically, an optical analog of a musical score of the pulse is produced by measuring its spectrogram. And the mathematics involved is equivalent to the two-dimensional phase-retrieval problem--a problem that is solvable only because the Fundamental Theorem of Algebra fails in two dimensions. We call the method Frequency-Resolved Optical Gating (FROG), and it is simple, rigorous, intuitive, and general. It can measure pulses in all spectral ranges, on a single-shot basis, and over a wide range of energies. FROG has been used to measure pulses as short as 4.5 femtoseconds (4.5 x 10-15 sec), and it can measure two pulses simultaneously. More recently, we have shown that FROG can be used in conjunction with spectral interferometry to measure essentially arbitrary pulses with as little as zeptojoules of energy (less than one photon!) on a multi-shot basis. |
| Friday, December 8, 2000 | Prof. A T. Johnson, Jr. [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | Univ. of Pennsylvania | |
| Physics Building | “Quantum Confinement of Electrons and Phonons in Single Wall Carbon Nanotubes” |
| Single wall carbon nanotubes are a fascinating set of nanomaterials whose unique physical properties reflect the effect of quantum confinement on the electronic and phonon energy spectrum. Electron waves confined to the cylindrical tube wall obey periodic boundary conditions. Their energy spectrum consists of a set of one-dimentional subbands, making nanotubes metals or semiconductors depending on the precise wrapping of the constituent graphene sheet. I will discuss functional nanotube devices we have made, including field effect transistors, diodes, and highly conducting electrical interconnects. Nanotube sound waves (phonons) also experience quantum size effects. This makes nanotubes incredibly stiff, and may enable mechanical composites or nano-mechanical systems. We recently measured the effect of the quantized phonon spectrum on the specific heat of nanotubes as well as their thermal conductivity. Our results support theoretical predictions that nanotubes have an extremely high thermal conductivity, perhaps the highest of any known material. |
| Friday, January 19, 2001 | Alan McKane [Host: Tim Newman] | |
| 4:00 PM, Room 204 | Department of Physics -University of Manchester, UK | |
| Physics Building | “Ecological dynamics of multispecies communities” |
| Many theoretical physicists with a background in non-equilibrium statistical mechanics are becoming interested in exploring mathematical models of ecosystems. The reason for this is clear when one realizes that such models typically involve a large number of individuals interacting according to simple rules and that the ultimate aim is to compute coarse-grained or long-time behavior. The ingredients of these models include population dynamics, predator-prey interactions, competitive effects, speciation and immigration. Two examples will be discussed. One is a model which describes the evolution of food webs using adaptive dynamics and the other, a stochastic model of species-rich ecosystems which makes predictions concerning the form of the species abundance distribution. |
|
Thursday, February 8, 2001 Note Special Day |
Jun Ye [Host: T. Gallagher] | |
| 4:00 PM, Room 204 | JILA | |
| Physics Building | “TBA” |
| Friday, February 9, 2001 | Nilanga Liyanage [Host: Gordon Cates] | |
| 4:00 PM, Room 204 | Jefferson Laboratory | |
| Physics Building | “Neutron Spin Structure Function Measurements at Jefferson Lab” |
| Spin structure functions provide basic information about the spin of the quark distributions inside the nucleon. Measurements at high energy laboratories have provided precision spin structure function data at low values of xbj. However, there is little precision data at low and moderate values of momentum transfer and high values of xbj . This is especially true for the neutron due to the absence of a free neutron target. Polarized ND3 , NH3 and 3He targets at Jefferson lab combined with its high-polarization continuous electron beam have provided the opportunity to make high precision neutron spin structure measurements in the high xbj region. As examples of high precision measurements possible at Jefferson lab, I will describe two planned neutron spin structure measurements, one in the deep inelastic region and the other in the resonance region, using the Hall A polarized 3He target. The deep inelastic measurement will provide the first precision test of predictions for the virtual photon asymmetry An1 in the valence quark region. The measurement in the resonance region, combined with the DIS measurement will provide a first test of quark-hadron duality for spin structure of the neutron |
| Friday, February 16, 2001 | Prof. Pulak Dutta [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | Northwestern Univ. | |
| Physics Building | “Nanoscale ordering in soft materials near surfaces and interfaces” |
| A material is 'soft' if its structure, and thus its properties, can change in response to very weak stimuli; hence the current interest in using soft materials for switching, sensing, etc. One way to induce structures that do not occur otherwise is with the help of a surface or interface. This talk will give some examples of the use of synchrotron radiation to look at how molecules self-organize near surfaces and soft-hard interfaces. Our studies of Langmuir monolayers (including their use as templates for inorganic nucleation), self-assembled films, and normal liquids near interfaces will be described. |
| Friday, February 23, 2001 | Jamie Nagle [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | Columbia University | |
| Physics Building | “First results from the Relativistic Heavy Ion Collider” |
| Friday, March 2, 2001 | B. Lee Roberts [Host: Blaine Norum] | |
| 4:00 PM, Room 204 | Boston University | |
| Physics Building | “Recent news from the vacuum? The Muon g-2 Experiment at Brookhaven” |
| Since the experiments of Stern and Gerlach, magnetic moments of "elementary" particles have been important in our quest to understand subatomic physics. A brief review of the history and foundations of this field will be given as an introduction to the muon g-2 experiment at the Brookhaven AGS. This experiment, E821, has recently reported a new result with a relative accuracy of 1.3 ppm, which is larger than the theoretical (Standard Model) value by 2.6 standard deviations. The physics context of this measurement, the experiment, and the analysis leading to this new result will be presented. |
| Friday, March 9, 2001 | Evelyn Patterson [Host: Steve Thornton] | |
| 4:00 PM, Room 204 | U. S. Air Force Academy | |
| Physics Building | “Using the World Wide Web for Physics Teaching and Learning: Exploring Where Pedagogy and Technology Meet” |
| The explosion of World Wide Web technology over the past several years has spurred the development of an ever-increasing number of web-based teaching and learning materials and techniques. Web technology is being used to support student-teacher, student-student, and teacher-teacher communications, often providing communications channels and possibilities not possible previously. At the same time, physics education research continues to provide more insight about how, why, and the extent to which our students do-- and don't-- learn physics. Can our research-based understanding of how students learn and the new unprecedented power of communications lead us to improved courses and programs? This talk will survey the spectrum of ways in which the web is being used by the physics education community to promote physics teaching and learning. It will also introduce and discuss a unique mix of pedagogy and the web technology, the "Just-in-Time Teaching" (JiTT) strategy, now being implemented by over 120 faculty at more than 60 institutions across the country and in Canada and Europe." |
| Friday, March 23, 2001 | William Wootters [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | Williams College | |
| Physics Building | “Quantum Entanglement as a Resource for Communication” |
| Quantum mechanical objects can exhibit correlations with one another that are fundamentally at odds with the paradigm of classical physics; one says that the objects are "entangled." In the past few years, entanglement has come to be studied not only as a marvel of nature but also as a potential resource, particularly as a resource for certain unusual kinds of communication. This talk reviews three proposed communication schemes based on entanglement: (i) dense coding, which is the effective doubling of the information-carrying capacity of a quantum particle through prior entanglement with a particle at the receiving end; (ii) teleportation, in which a quantum state is transferred from one particle to another over a distance, apparently without traversing the intervening space; and (iii) the efficient pooling of classical data, in which separated participants arrive at a conclusion faster because they share entanglement. These three schemes highlight three distinct ways in which entanglement can enhance communication. |
| Friday, March 30, 2001 | Professor Hongxing Jiang [Host: E. Kolomeisky and J. Poon] | |
| 4:00 PM, Room 204 | Kansas State | |
| Physics Building | “III-Nitride Micro- and Nano-Structures and Devices” |
| Advances in materials research and novel structure designs have brought the dimensions of photonic devices to the scales of the wavelength of the light they emit, transmit, and detect. In this realm, quantum nature of light dominates, enabling more efficient and fast devices. In this talk, the fabrication and optical studies of micron and wavelength-scale photonic structures, including micro-cavities and micro-size light emitters, based on III-nitride wide bandgap semiconductors will be presented. Our recent work on sub-micron photonic structures prepared by e-beam lithography and plasma etching will be discussed. Potential applications of III-nitride micro- and nano-photonics in efficient energy conversion and optical communications will be also be summarized. |
| Friday, April 20, 2001 | Hank Thacker [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “How QCD Works” |
| Mathematically, the interaction between quarks and gluons is remarkably similar to the electromagnetic interaction of electrons and photons. But unlike QED, QCD has an essentially nonperturbative structure, as exhibited most strikingly by the absolute confinement of quarks, which represents a fundamental property of the QCD vacuum (complete screening of color charge). Another property of QCD, chiral symmetry breaking, is also a statement about the vacuum, i.e. that it is full of quark-antiquark pairs (analogous to Cooper pairs in BCS theory). Chiral symmetry breaking and quark confinement are probably related phenomena, but the connection is poorly understood. I will discuss recent lattice calculations which have begun to expose the structure of the QCD vacuum. |
| Friday, April 27, 2001 | Brian Cole [Host: C. Dukes] | |
| 4:00 PM, Room 204 | Columbia University | |
| Physics Building | “The Baryon Junction and High-Energy Nuclear Collisions” |
| In the 1970's Veneziano suggested the existence of a set of diagrams in Regge theory that could allow the baryon number to be "extracted" from a baryon in a single step in high-energy hadronic interactions. Because no experimental evidence for these diagrams was found, the idea was largely forgotten. However, in recent years it has been resurrected and re-cast in terms of the so-called "baryon junction" a (possible) non-perturbative topological defect in the gluon fields within the baryon. In this picture, the junction plays the role of "bookkeeper" for baryon number conservation in high-energy collisions. Current theoretical models suggest that diagrams involving the exchange of the junction only become important in hadronic (e.g. p-p) collisions at collider energies. However, the junction may become active at much lower energies in nuclear collisions due to the multiple interaction of the incident nucleons. I will use results from a new generation of experiments studying proton-collisions at the Brookhaven National Laboratory AGS and CERN SPS accelerators to illustrate the possible role played by the junction in the "stopping" of the protons and in the abundant production of strange baryons and the production of anti-baryons. I will then discuss the possibility that the junction may be responsible for some of the anomolous results obtained from fixed-target heavy-ion experiments at the CERN SPS that were recently argued to provide evidence for quark-gluon plasma formation in high-energy nuclear collisions. I will discuss future studies of junction physics in fixed-target proton-nucleus experiments and in proton-proton and proton-nucleus collisions at the Relativistic Heavy Ion Collider. I will finish by highlighting some recent speculation that novel states of matter formed from "meshes" of junctions and anti-junctions may be created in heavy-ion collisions at RHIC. |
|
Thursday, May 3, 2001 Note Special Day |
Pierre Pillet [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | Laboratoire Aime Cotton | |
| Physics Building | “Formation and Trapping of Ultracold Molecules by Photoassociation” |
| Friday, May 4, 2001 | Dr. Jeff Appel [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Fermilab | |
| Physics Building | “The Fixed-Target Charmed Road to Understanding Hadrons” |
| Measurements involving charm quarks tell us about the nature and details of light hadrons. This talk will summarize how and what we are learning from charm fixed-target experiments about the usual ground-state hadrons, and about scalar resonances such as the sigma, kappa, and f_0's which have had uncertain histories so far. |
| Friday, May 11, 2001 | Professor James Stone [Host: Robert Jones] | |
|
11:00 AM, Room 204 Note Special Time |
Boston University and Department of Energy | |
| Physics Building | “A Study of Atmospheric Neutrinos with the Super-Kamiokande Detector” |
| The observation of flavor oscillations in atmospherically produced neutrinos by the Super-Kamiokande Experiment represents the first indication of massive neutrinos and new physics beyond the Standard Model of Particle Physics. Neutrino physics in the context of oscillations will be discussed and a detailed description of the Super-Kamiokande detector will be presented. The latest experimental results on proton decay, atmospheric and long baseline neutrino studies will be shown. |
| Friday, September 7, 2001 | J. Elkins [Host: T. Gallagher] | |
| 4:00 PM, Room 204 | National Oceanic and Atmospheric Administration | |
| Physics Building | “A Problem in Atmospheric physics: Stratospheric ozone depletion” |
| Since 1987, almost all countries have signed the Montreal Protocol to control substances that cause depletion of the ozone layer. One of the successes of the Protocol has been the dramatic decrease in emissions of methyl chloroform, a metal degreaser that has been responsible for the decline of total equivalent chlorine in the atmosphere. However, chlorofluorocarbon (CFC-12), a common refrigerant, and the halons, fast-acting fire extinguishing agents, are still increasing in the atmosphere even though production ceased for the developed countries in 1996. This research talk will discuss ground-based and airborne measurements and their implication for the future ozone depletion. Preliminary results from a recent field campaign operated on the Trans-Siberian Railway will also be presented. |
| Friday, September 14, 2001 | Puru Jena [Host: Lou Bloomfield and Joe Poon] | |
| 4:00 PM, Room 204 | Virginia Commonwealth University , Richmond, VA - Department of Physics | |
| Physics Building | “TheRole of Clusters in the Design of Nano-Scale Systems” |
| Atomic clusters consisting of a few to a few thousand atoms constitute a new phase of matter intermediate between atoms and solids. Unlike conventional nanostructured materials, the size and composition of these clusters can be controlled one atom at a time. The properties of such clusters brought about by their large surface-to-volume ratio, unique geometry, low dimensionality and reduced coordination, exhibit novel behavior quite unlike that in the bulk. For example, metallic elements can be made to form ionic bonds while nonmagnetic and anti-ferromagnetic materials can become ferromagnetic or ferrimagnetic. This talk will introduce the principles for designing these clusters and discuss a concept where clusters can be viewed as super-atoms - adding a third dimension to the periodic table. Recent experimental evidence to support this idea will be presented. Examples of cluster assembled materials will include high-energetic materials involving Al(MnO4)3, alkali metal clusters isolated in zeolites, transition metal clusters supported on organic and metallic substrates, and manganese-oxide clusters passivated by acetate ligands. Ultimately the properties of crystals composed of clusters as the building blocks will be discussed. It is hoped that the synergy between theory and experiment will lead to the synthesis of cluster assembled materials with unique and tailored properties, thus creating new opportunities in materials science at the dawn of the new millennium. |
| Friday, September 21, 2001 | Jun Ye [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | JILA | |
| Physics Building | “Light: Time meets frequency” |
| Friday, September 28, 2001 | Krishna Rajagopal [Host: Peter Arnold] | |
| 4:00 PM, Room 204 | MIT | |
| Physics Building | “From the QCD Phase Diagram to Heavy Ion Collisions and Back” |
| I describe some of the things we think we know about the physics of a hot quark-gluon plasma and the phase transition between the stuff of the big bang and ordinary hadronic matter. The questions I will pose motivate people to collide heavy ions at relativistic energies. I will give two examples of how we may use measurements made in these experiments to map the QCD phase diagram, and hence to study the condensed matter physics of QCD. |
| Friday, October 5, 2001 | Arthur S. Brill [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Hyperfine physics - from the hydrogen atom to hemoglobin” |
| Hyperfine physics deals with interactions between electron and nuclear spins. Measurements of these interactions provide information about the electronic structure of paramagnetic sites in molecules and crystals. Examples will be presented and briefly discussed of the roles of such measurements in atomic, biological, condensed matter molecular and nuclear physics. |
| Friday, October 12, 2001 | David F. Anderson [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | Fermi National Accelerator Laboratory | |
| Physics Building | “Understanding Flight” |
| Through the years the explanation of flight has become mired in misconceptions that have become dogma. Wolfgang Langewiesche, the author of "Stick and Rudder" (1944) got it right when he wrote: "Forget Bernoulli's Theorem". A wing develops lift by diverting (from above) a lot of air. This is the same way that a propeller produces thrust and a helicopter produces lift. Newton's three laws and a phenomenon called the Coanda effect explain most of it. With an understanding of the real physics of flight, many things become clear. Inverted flight, symmetric wings, and the flight of insects are obvious. It is easy to understand the power curve, high-speed stalls, and the effect of load and altitude on the power requirements for lift. The contribution of wing aspect ratio on the efficiency of a wing, and the true explanation of ground effect will also be discussed. |
| Friday, October 19, 2001 | Michael Widom [Host: Joe Poon] | |
| 4:00 PM, Room 204 | Carnegie Mellon University | |
| Physics Building | “Entropy in the Solid State” |
| Equilibrium states of matter balance the thermodynamic tendency to minimize energy with the simultaneous need to maximize their entropy. Depending on the temperature, different equilibrium states may occur representing different tradeoffs between energy and entropy, leading potentially to a multiplicity of solid state phases. The phase diagram of a superalloy and of the element Pu illustrate the importance of entropy residing in modes of atomic vibrations. Additional examples will be given of quasicrystal- and glass-forming alloys in which the entropy resides instead in novel discrete configurational degrees of freedom. |
| Friday, October 26, 2001 | G. 't Hooft [Host: P. K. Kabir] | |
| 4:00 PM, Room 204 | University of Utrecht, Netherlands | |
| Physics Building | “How does God Play Dice? (Speculations about Quantum Mechanics at the Planck scale)” |
| Attempts to arrive at consistent theories combining Quantum Mechanics with General Relativity not only require new concepts of space, time and matter, such as the ideas that lead to Superstring Theory, D-brane theory and M-theory, but they may also require a reconsideration of what Quantum Mechanics itself really is about. Although completely deterministic scenarios appear to be ruled out by the Bell inequalities, it is nevertheless worth-while to investigate a set-up where we start with a deterministic theory and add to this the notion of information loss. Although models proposed so-far all show deficiencies of some sort which makes them unrealistic for describing the real world, these models do show how chaotic phenomena in a deterministic theory might be suspected to lie at the basis of the quantum nature of our world. |
|
Monday, October 29, 2001 Note Special Day |
Gerald 't Hooft [Host: Department of Physics] | |
|
7:30 PM, Room 402 Note Special Time |
University of Utrecht | |
| Chemistry Building | “The Universe of the Elementary Particles” |
| Friday, November 2, 2001 | Chris Monroe [Host: Robert Jones] | |
| 4:00 PM, Room 204 | University of Michigan | |
| Physics Building | “Building a quantum computer atom by atom” |
| A quantum computer can store and process quantum superpositions of numbers. This parallelism leads to an exponential speedup over conventional computers for certain algorithms. However, the prospects for constructing a quantum computer are highly speculative, owing to the extremely fragile nature of quantum superpositions. A quantum computer is nothing more than a smaller (and more humane) version of Schroedinger's Cat, and if one is ever built, it will strongly impact both computer science and fundamental quantum mechanics. A leading physical candidate for a quantum computer is a collection of individual trapped atoms, controlled and manipulated with optical fields. Experiments are reported in this context, including the demonstration of simple quantum logic gates and the controlled generation of entangled quantum states. The outlook for future quantum computing with atoms or alternative technologies will be discussed. |
| Friday, November 9, 2001 | Mariano Quiros [Host: P. Q. Hung] | |
| 4:00 PM, Room 204 | Istituto de Estructura de la Materia (CSIC), Madrid, Spain | |
| Physics Building | “The Long Way From Strings To Large Extra Dimensions ” |
| In the first part of the talk I will review the main ideas going from string models to the possibility of low string scales and large extra dimensions. In particular the subjects of bosonic and fermionic strings (IIA, IIB, heterotic and type I/I'), T-duality and D-branes, will be covered. In the second half of the talk I will describe the different scales which can appear in the various string constructions and provide the experimental constraints on transverse (gravitational) and longitudinal (gauge) dimensions using gravitational and collider data. |
| Friday, November 16, 2001 | Michael Duff [Host: P. Q. Hung] | |
| 4:00 PM, Room 204 | University of Michigan | |
| Physics Building | “A Layman's Guide To M-Theory” |
| Superunification of the fundamental interactions underwent a major paradigm shift in 1984 when eleven-dimensional supergravity was knocked off its pedestal by ten-dimensional superstrings. 1995 witnessed another shift of equal proportions, however, when superstrings were themselves superseded by ``M-theory'', a non-perturbative theory which describes extended objects with two dimensions (supermembranes) and five dimensions (superfivebranes), which subsumes all five consistent string theories and whose low-energy limit is, ironically, eleven-dimensional supergravity. |
| Friday, November 30, 2001 | Andrew Hime [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | Los Alamos | |
| Physics Building | “Results from the Sudbury Neutrino Observatory” |
| The Sudbury Neutrino Observatory (SNO) is a heavy water, imaging Cerenkov detector operating 6800 feet underground in the Creighton Nickel Mine in Ontario, Canada. With its heavy water target, SNO has the unique capability to detect and separate three distinct 8B solar neutrino signals through the charged current (CC), neutral current (NC), and elastic scattering (ES) channels. By comparing the solar neutrino flux deduced from the CC interaction (sensitive only to electron neutrinos) with that deduced from the NC or ES interactions (sensitive to all active neutrino flavors), SNO can make a unique study of the solar neutrino deficit and a model independent test for neutrino oscillations. Results from the pure D2O phase of SNO will be presented along with their implications for elementary particle physics, astrophysics, and cosmology. |
| Friday, December 7, 2001 | Swapan Chattopadhyay [Host: Donal Day] | |
| 4:00 PM, Room 204 | JLAB | |
| Physics Building | “New Dimensions in Probing the Structure and Function of Matter: Concepts, Techniques and Technologies” |
| We will explore various concepts, techniques and technologies for producing ultrashort pulses of electrons and photons of all energies and colors from the femtosecond to the attosecond duration and beyond for breakthrough research in physics, chemistry, life and information sciences |
| Friday, January 18, 2002 | Daniel Gammon [Host: O. Pfister] | |
| 4:00 PM, Room 204 | Naval Research Lab. | |
| Physics Building | “Optically probing and controlling a single quantum dot” |
| Friday, January 25, 2002 | Olivier Pfister [Host: T. Gallagher] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Quantum information with quantum fields: creation and entanglement of twin beams of light” |
| The concept of quantum information can be seen as stemming from the fascinating idea of putting quantum mechanics to practical use as such, and not only as the theory behind, in particular, microscopic physics. Because of the latter, it is sometimes believed that experimental efforts in quantum information only involve exquisite control over nanoscale entities such as single atoms or single photons (see last week's colloquium for a beautiful illustration). This is not rigorously true, as qubits can also be implemented using exquisitely controlled macroscopic entities, such as optical fields of milliwatt power. In this talk, I will present our endeavor to create bright entangled light sources suitable for quantum teleportation and quantum error correction, as well as our contribution to the theoretical understanding of such problems. |
| Friday, February 1, 2002 | Michael Turner [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | University of Chicago | |
| Physics Building | “Making Sense of the New Cosmology” |
| Cosmology is in its most exciting period of discovery yet. Over the past five years we have determined the basic features of the Universe -- spatially flat; accelerating; composed of 1/3rd a new form of matter, 2/3rds a new form of energy, with some ordinary matter and neutrinos; and apparently born from a burst of rapid expansion during which quantum noise was stretched to astrophysical size seeding cosmic structure. Now we have to make sense of this: What is the dark matter particle? What is the nature of the dark energy? Why this mixture? How did the matter -- antimatter asymmetry arise? What is the underlying cause of inflation (if it occurred)? If we succeed in making sense of our Universe, this will truly be remembered as a Golden Age. |
| Friday, February 8, 2002 | Jun Ye [Host: T. Gallagher] | |
| 4:00 PM, Room 204 | JILA | |
| Physics Building | “Light: Time Meets Frequency” |
| Friday, February 15, 2002 | Despina Louca [Host: T. Gallagher] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Lattice Effects and Jahn-Teller Fluctuations in Crystals” |
| In many systems i.e. magnetoresistive and superconducting oxides, the atomic structure couples strongly to the electronic degrees of freedom. In CMR crystals, Jahn-Teller effects are strongly related to the metal-insulator transition, for instance. The manganites are one example where the JT distortions are static and are important ingredients to the polaron lattice formation. In cuprates, when static distortions are present it usually means superconductivity is killed, while dynamic effects prevailing in the SC phase are sometimes too fast to observe. (La/Sr)CoO3 serves as a prototype for studying the crossover from static to dynamic effects. With the pair density function analysis and inelastic S(Q,w) measurements, it was determined that dynamical JT fluctuations induce a distorted atomic structure. The S(Q,w) clearly shows the presence of localized phonon modes most likely due to JT excitations, while the local structure transforms to an unusually glassy state that is intermediate to the manganites and cuprates. |
| Friday, February 22, 2002 | Kareljan Schoutens [Host: Paul Fendley] | |
| 4:00 PM, Room 204 | University of Amsterdam | |
| Physics Building | “New States of Matter in the Quantum Hall and BEC Regimes ” |
| Friday, March 1, 2002 | N.O. Lipari [Host: V. Celli] | |
| 4:00 PM, Room 204 | Lipari Int'l Consulting | |
| Physics Building | “Physicists and Industry in the 21st Century: Who, What, How” |
| The on-going global economic transformations require that industries strongly focus on innovation, time to market, quality and cost in the introduction of new products. The trend in each industry is to focus on core competencies and obtain the additional resources from external alliances and partnerships with Universities and Government. "Coopetition" is emerging as the most effective approach for technology transfer, i.e. the path from idea to products. This requires a totally different and much more pervasive role of the physicist. In addition to the scientific skills, the scientist needs interdisciplinary and communication skills in order to successfully interact in the industrial environment. Examples will be given. Specific suggestions for the role of the university in forming the physicists with the proper requirements for the modern industry will be discussed. |
| Friday, March 8, 2002 | Julian Noble [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Running Out of Time: Why Elephants Don't Gallop” |
| Newtonian physics implies that running is impossible for sufficiently large animals. There are two main factors that influence this: 1. An animal's strength/weight ratio decreases with size, hence a sufficiently large animal will be liable to injury if it attempts a gallop. 2. The time required for an animal to move its limbs increases with size, but the time an animal can remain in the air (while running) does not scale with linear dimension. Therefore there is some size beyond which an animal has "run out of time" and cannot take advantage of a running gait. These aspects of the biomechanics of locomotion bear on the interesting questions of determining the speeds of extinct species, as well as how varying gravity affects locomotion. |
| Friday, March 22, 2002 | Dr. Bruce Van Dover [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | Agere Systems , Murray Hill NJ | |
| Physics Building | “High-performance dielectric thin films for science and technology” |
| Ultrahigh-density dynamic random acess memory, hyperscaled field-effect transistors, and field-effect-induced superconductivity at 117 K in fullerenes are examples where high-performance thin film dielectrics play a pivotal role in science and technology. In the past, only a small set of materials (SiO2, Al2O3, (Ba,Sr)TiO3, etc.) have been considered for these structures. We have assessed a wide range of dielectric systems using a high-throughput, composition-spread approach. This has lead to the discovery and development of dielectrics with extremely high performance, as well as the identification of unexpected physics by careful investigation of systematic trends. I will discuss the scientific and technological issues, our approach to discovery, and the interesting materials and materials physics we have uncovered. |
| Friday, March 29, 2002 | A. Marchionni [Host: S. Conetti] | |
| 4:00 PM, Room 204 | Fermi Lab | |
| Physics Building | “Long baseline neutrino oscillation experiments: why and how” |
| The evidence for neutrino oscillations from the SuperKamiokande experiment still leaves several open questions. The present program of long baseline neutrino oscillation experiments will address these issues. The ongoing K2K experiment and the future JHF facility in Japan, the programs in preparation in the United States (MINOS) and in Europe (CNGS) will be reviewed. MINOS (Main Injector Neutrino Oscillation Search) will be operating at the beginning of 2005 over a baseline of 735 km from FERMILAB (Illinois) to Soudan (Minnesota). Status and goals of the MINOS experiment will be reported in detail. |
| Friday, April 12, 2002 | Thomas Gallagher [Host: Eugene Kolomeisky] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Spontaneous evolution from a cold Rydberg gas to an ultra cold plasma” |
| Friday, April 19, 2002 | Larry Cardman [Host: T. Gallagher] | |
| 4:00 PM, Room 204 | JLab | |
| Physics Building | “Building Nucleons and Nuclei from Quarks and Glue: Early Results from the Research Program at Jefferson Lab” |
| Friday, April 26, 2002 | Sidney A. Coon [Host: S. Liuti] | |
| 4:00 PM, Room 204 | NSF and New Mexico State University | |
| Physics Building | “A Singular Potential:from Theorist's Toy to Experimental Realization” |
| The inverse square potential (V(r)~1/r**2), first studied by Cote, a contemporary of Isaac Newton, is an interesting potential for nonrelativistic quantum mechanics. It lies on the edge of the line dividing potentials which can be treated in the familiar manner and those which are singular. Singular potentials have been studied for a long time because they can be regarded as models for nonrenormalizable field theories, and, more recently, as an element of the new paradigm of effective field theory methods in nuclear physics. In this talk, I will demonstrate the mathematics of the 1/r**2 potential, including the anomalous (quantum mechanical) breaking of scale symmetry and a rigorous treatment of absorption ("fall to the center"). Correct mathematics leads to a quantum mechanical understanding of the formation of anions (electrons bound by the dipole moment of a polar molecule) and of a very recent dedicated experimental study of this potential in the context of manipulation of cold atoms. |
| Friday, September 13, 2002 | Prof. Puru Jena [Host: Joseph Poon/Louis Bloomfield] | |
| 4:00 PM, Room 204 | Virginia Commonwealth University | |
| Physics Building | “The Role of Clusters in the Design of Nano-Scale Systems” |
| Atomic clusters consisting of a few to a few thousand atoms constitute a new phase of matter intermediate between atoms and solids. Unlike conventional nanostructured materials, the size and composition of these clusters can be controlled one atom at a time. The properties of such clusters brought about by their large surface-to-volume ratio, unique geometry, low dimensionality and reduced coordination, exhibit novel behavior quite unlike that in the bulk. For example, metallic elements can be made to form ionic bonds while nonmagnetic and anti-ferromagnetic materials can become ferromagnetic or ferrimagnetic. This talk will introduce the principles for designing these clusters and discuss a concept where clusters can be viewed as super-atoms - adding a third dimension to the periodic table. Recent experimental evidence to support this idea will be presented. Examples of cluster assembled materials will include high-energetic materials involving Al(MnO4)3, alkali metal clusters isolated in zeolites, transition metal clusters supported on organic and metallic substrates, and manganese-oxide clusters passivated by acetate ligands. Ultimately the properties of crystals composed of clusters as the building blocks will be discussed. It is hoped that the synergy between theory and experiment will lead to the synthesis of cluster assembled materials with unique and tailored properties, thus creating new opportunities in materials science at the dawn of the new millennium. |
| Friday, September 20, 2002 | Greg Landsberg [Host: P. Q. Hung] | |
| 4:00 PM, Room 204 | Brown University | |
| Physics Building | “Black Holes at Future Colliders and Beyond” |
| If the scale of quantum gravity is as low as a TeV, as was proposed by Arkani-Hamed, Dimopoulos, and Dvali a few years ago, one of the most dramatic manifestation of this fact would be copious production of miniature black holes at the CERN's LHC accelerator, qualifying the latter as black-hole factories. These rapidly evaporating black holes could serve as sensitive probes of quantum gravity effects, topology of extra dimensions, and as a laboratory to produce new particles with the mass ~100 GeV. I'll discuss the black hole production and decay mechanisms at future colliders and the opportunities of cosmic ray detectors in observing black holes in ultra-high-energy cosmic ray collisions. Using the Higgs boson as an example, I'll demonstrate that it can be found in the decays of black holes as early as in the first hour of operation of the LHC, even with incomplete detectors. |
| Friday, October 4, 2002 | Professor Paul Avery [Host: Brad Cox] | |
| 4:00 PM, Room 204 | University of Florida | |
| Physics Building | “Global Data Grids for Data Intensive Science” |
| Friday, October 18, 2002 | Siyuan Han [Host: B. Shivaram] | |
| 4:00 PM, Room 204 | Department of Physics and Astronomy, University of Kansas | |
| Physics Building | “Superconducting Schrodingers Cat and its Application to Quantum Computing” |
| Since the beginning days of quantum mechanics the possibility of having coherent superposition of macroscopic quantum states, e.g., Schrodingers Cat, has stimulated much theoretical debates. The idea can actually be tested out experimentally in superconducting electronic devices called Josephson junctions (JJs) and SQUIDs. Ill show that when sufficiently isolated from environments a current biased JJ is a very well characterized and controllable macroscopic quantum system and that Rabi oscillations can be utilized to create coherent superposition of macroscopic quantum states. In a recent experiment, we have succeeded in placing a JJ in the superposition of its ground (alive) and excited (dead) states and observing its time evolution as it oscillates coherently between the alive and dead states of the junction [Y. Yu et al., Science 296, p889 (May 2002)]. The coherence time, estimated from the exponentially decaying amplitude of the oscillations, is about 5 s which is very promising for quantum computing using the phase qubits (JJs) or flux qubits (SQUIDs). |
| Friday, October 25, 2002 | Randy Hulet [Host: Cass Sackett] | |
| 4:00 PM, Room 204 | Rice University | |
| Physics Building | “Tunable Interactions in Ultracold Bose and Fermi Gases - Solitons to Superfluids” |
| Bose-Einstein condensation of ultracold atomic gases, first achieved only seven years ago, has lead to remarkable demonstrations of matter wave phenomena. One of the most compelling aspects of ultracold atoms is the experimental ability to alter the strength and even the sign of the interactions between atoms using magnetically tuned "Feshbach resonances". We have exploited this tunability to create matter wave solitons composed of Bose-Einstein condensates of lithium atoms [1]. A similar experiment was performed in Paris [2]. Soliton waves arise when a nonlinearity exactly compensates for wavepacket dispersion. This compensation enables a soliton to propagate without spreading. Solitons are observed in a variety of physical systems, including water waves, plasma waves, and optical pulses, to name but a few. The nonlinearity in ultracold atoms arises from their interactions. By changing the interactions from repulsive to attractive, the condensate is observed to form a multi-soliton "train" of up to 15 individual solitons. The solitons maintain their size and shape for a propagation time of up to 3 s. Adjacent solitons are observed to interact repulsively. We are also pursuing the possibility of creating Cooper pairs of fermionic 6Li atoms, which would be an atom analog of superconductivity, in the gas phase. The necessary attraction would again be generated using a Feshbach resonance, which could enable the first exploration of superconductivity in the strong coupling regime. [1] K.E. Strecker, G.B. Partridge, A.G. Truscott, R.G. Hulet Nature 417, 150 (2002). [2] L. Khaykovich et al., Science 296, 1290 (2002). |
| Friday, November 8, 2002 | Jerry Blazey [Host: Bob Hirosky] | |
| 4:00 PM, Room 204 | NIU | |
| Physics Building | “Physics at DZERO: Exploring the Microscopic Structure of the Universe” |
| To explore the microscopic structure of the universe very energetic beams of submicroscopic particles and complicated detectors, such as the DZERO detector, are required. These huge machines, built by graduates students, physicists, and engineers, have the potential to explain the origins of mass and to explore extra spatial dimensions. The technology behind these investigations and their current state will be described. Prof. Blazey serves as spokesman for the D-Zero Collaboration at Fermilab and director of NICADD, the Northern Illinois Center for Accelerator and Detector Development. |
| Friday, November 15, 2002 | Konstantin Matveev [Host: Eugene Kolomeisky] | |
| 4:00 PM, Room 204 | Duke University | |
| Physics Building | “ 0.7-anomaly in Quantum Point Contacts A” |
| A remarkable property of one-dimensional conductors is the quantization of their resistance in units of Planck constant divided by the square of the elementary charge. This effect is well understood and readily observed in low-temperature experiments with relatively short one-dimensional conductors called the quantum point contacts. A puzzling feature of the transport through such contacts was reported a few years ago, when it was discovered that at somewhat higher temperatures the conduction drops to about 0.7 of its quantized value. This phenomenon, often referred to as the 0.7-anomaly, has been studied extensively in the last few years. I will discuss the latest experimental data and the theoretical attempts at understanding this effect. |
| Friday, November 22, 2002 | David DeMille [Host: Cass Sackett] | |
| 4:00 PM, Room 204 | Yale | |
| Physics Building | “Tabletop probes for TeV physics: searches for the electric dipole moment of the electron” |
| Remarkably, the virtual exchange of exotic heavy particles--such as those predicted to exist in supersymmetric and grand unified theories-- can lead to observable effects in ordinary matter. This talk will describe a set of experiments searching for such an effect: namely, a permanent electric dipole moment along the spin of the electron. The most sensitive experiments of this type are already sensitive to new physics at the TeV scale, and set important limits on possible extensions to the standard model. I will report on our progress in developing a new technique, which promises several orders of magnitude improvement in sensitivity. |
| Friday, January 24, 2003 | David Divincenzo [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | IBM | |
| Physics Building | “Prospects for Quantum Computation” |
| A "standard model" for the physical implementation of a quantum computer was laid out some years ago. It indicated a set of capabilities that had to be achieved to make quantum processing possible: 1) systems with well-characterized qubits must be constructed. 2) These qubits should be initializable to the "0" state. 3) It must be possible to control the one- and two-qubit Hamiltonian of the system, so that unitary quantum logic gates are enacted. 4) Decoherence and imprecision of gate operations must be kept very low. 5) Reliable measurements of the quantum state of individual qubits must be possible. In this talk I will indicate progress towards these goals, after first reviewing why we want to do quantum computation. |
| Friday, January 31, 2003 | Amy Bug [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | Swarthmore College | |
| Physics Building | “Gender and Physics: a Hard Look at a Hard Science” |
| Friday, February 7, 2003 | Rolf Sharenberg [Host: Ken Nelson] | |
| 4:00 PM, Room 204 | Purdue University - (E-735 Collaboration) | |
| Physics Building | “Experimental evidence for hadronic deconfinement in pbar-p collisions at 1.8 TeV” |
| We have measured deconfined hadronic volumes, 4.4 < V < 13.0 fm3, produced by a one dimensional (1D) expansion. These volumes are directly proportional to the charged particle pseudorapidity densities 6.75 < dNc/d0 < 20.2. The hadronization temperature is T = 179.5±5(syst) MeV. Using Bjorken's 1D model, the hadronization energy density is F = 1.10±0.26(stat) GeV/fm3 corresponding to an excitation of 24.8±6.2(stat) quark–gluon degrees of freedom. |
| Friday, February 14, 2003 | Robert Bryant [Host: Bascom Deaver] | |
| 4:00 PM, Room 204 | UVA - Chemistry | |
| Physics Building | “Nuclear Spin Relaxation, Dispersion, and Intermolecular Exploration” |
| Friday, February 21, 2003 | Philip Phillips [Host: Jongsoo Yoon] | |
| 4:00 PM, Room 204 | UIUC | |
| Physics Building | “The Illusive Bose Metal” |
| Cooper pairs (bosons) are thought to exist in two quite distinct ground states: 1) localized in a Mott insulator or 2) condensed in a superconductor. However,recent experiments on 2D insulator-superconductor transitions indicate that there may be a third possibility: a metal with a finite resistivity at zero temperature. I will review the standard theoretical framework used to understand the insulator-superconductor transition, the recent experimental results and I will show quite generally how bosons lacking phase coherence can form a metal in the presence of disorder rather than an insulating phase. The metallic state is rather weird, however. The phase degrees of freedom are glassy. At the heart of the metallic state is the dissipation inherent in the glassy state. Bosons moving in such a glassy environment fail to localise because no true ground state exists. |
| Friday, March 14, 2003 | Dinko Pocanic [Host: Eugene Kolomiesky] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “A new look at rare pion and muon decays” |
| Pion and muon, the lightest unstable particles, were discovered more than fifty years ago, and have been well studied since. However, over time the Standard Model (SM) of elementary particles and interactions has become so successful that for several key pion and muon properties its predictions are far less uncertain than the best available measurements, primarily those concerning the particles' rare decay modes. Thus, slight deviations from the SM predictions can provide valuable clues to new physics outside of the current SM.
In its first phase, the PIBETA experiment has measured accurately several such rare decays at PSI, the Swiss meson facility. The talk will focus on the motivation, experimental apparatus, method, and the unexpected first results of these measurements. |
| Friday, March 21, 2003 | Ganpathy Murthy [Host: Eugene Kolomeisky] | |
| 4:00 PM, Room 204 | University of Kentucky | |
| Physics Building | “Interactions and Disorder in Quantum Dots: A New Large-g Approach” |
| Understanding the combined effects of disorder and interactions in electronic systems has emerged as one of the most challenging theoretical problems in condensed matter physics. It turns out that one can solve this problem non-perturbatively in both disorder and interactions in the regime when the system is finite (as in a quantum dot) but its dimensionless conductance g under open-lead conditions is large. This regime is experimentally interesting for the statistics of Coulomb Blockade in quantum dots and persistent currents in rings threaded by a flux. First some RG work will be described which shows that a disordered quantum dot with Fermi liquid interactions can be in one of two phases; one controlled by the so-called Universal Hamiltonian and another regime where interactions become large. These two are separated in the infinite-g limit by a second-order phase transition. I will show how to solve for the strong-coupling phase, which is characterized by a Fermi surface distortion, by a large-N approximation (where N=g is in fact large for realistic systems). Predictions will be presented for finite but large g for the statistics of the Coulomb Blockade peak spacings and other correlators. Finally, the relationship of these results to puzzles in persistent currents in mesoscopic rings will be presented. |
| Friday, April 4, 2003 | Leslie Camilleri [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | Fermilab/CERN | |
| Physics Building | “The Fascination of Neutrino Oscillations: Their discovery and their future study” |
| Anomalies have been observed in both solar and atmospheric neutrinos. How the study of these anomalies has led to the discovery of neutrino oscillations will be summarized. Many experiments are now being built to further our understanding of these oscillations. These experiments, and the next generation of experiments being planned to complete our understanding of how neutrinos mix and what their mass spectrum is, will be described. |
| Friday, April 11, 2003 | Sean Washburn [Host: Joseph Poon] | |
| 4:00 PM, Room 204 | University of North Carolina at Chapel Hill | |
| Physics Building | “Nanotechnology, nanotubes and molecules as tinker toys” |
| Nanotechnology holds many promises for the future and many (possibly insurmountable) challenges before the promises can be implemented. Carbon nanotubes with their superb mechanical and electrical properties are a canonical example of both of these aspects. The possibility of assembling them into designed forms as new materials or or into nanometer mechanical and electrical devices might lead to improved strengths, speeds, etc. Some elementary experiments indicate that while the promise is still great, the barriers to implementing such nano-devices are still ahead of us. The methods of the experiments already have shown that many academic disciplines and new techniques will be involved in invoking the new improvements. Some examples of such efforts will be reviewed. |
| Friday, April 18, 2003 | Tom Abel [Host: P. Q. Hung] | |
| 4:00 PM, Room 204 | Pennsylvania State Univ. | |
| Physics Building | “The First Stars in the Universe” |
| Recent progress in our ability to follow numerically the formation of the first objects in the universe predict the first stars to massive and to form in isolation. They are copious producers of UV radiation and begin to reionize the intergalactic medium. The single currently allowed model for structure formation turns out to be able to match all aspects of the most recent accurate measurements of the cosmic microwave background radiation. In this talk we highlight our new understanding of the physics of the formation of the first stars, their lifes, their remnants and their impact on subsequent structure formation. |
| Friday, April 25, 2003 | Prof. John Malko [Host: Oscar Rondon] | |
| 4:00 PM, Room 204 | Emory University | |
| Physics Building | “How a doctor of particle physics found happiness working with 'real doctors'” |
| Friday, September 12, 2003 | Professor Chris Quigg [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Fermi National Accelerator Laboratory | |
| Physics Building | “Envisioning Particles and Interactions” |
| I will present a new way to envision the particles and interactions: a pair of interpenetrating tetrahedra that we might call the double simplex, in homage to the double helix that has just celebrated its fiftieth anniversary. Any chart or mnemonic device should be an invitation to narrative and a spur to curiosity, and that is what I intend for the double simplex. My goal is to represent what we know is true, what we hope might be true, and what we don't know--in other terms, to show the connections that are firmly established, those we believe must be there, and the open issues. I want also to express the spirit of play, of successive approximations, that animates the way scientists work. |
| Friday, October 10, 2003 | Herb Fertig [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | University of Kentucky | |
| Physics Building | “The Quantum Hall Bilayer: A New Superfluid” |
| Superfluids and superconductors are known to possess a unique stiffness related to the phase of their groundstate wavefunctions. Under appropriate circumstances, double layer quantum Hall systems possess an analogous stiffness that may be understood in terms of a condensation of particle-hole pairs. The relation between these systems has motivated both theoretical and experimental efforts to find properties in the bilayer quantum Hall system usually associated with superfluids. Most prominently, an effect reminiscent of Josephson tunneling has been observed in experiments with high quality samples, although there is considerable dissipation whose origin is not understood. Using a renormalization group analysis and results from Langevin dynamics simulations, we demonstrate that the likely source of dissipation is vortices in the phase degree of freedom. Vortex pairs are shown to have a very unusual thermal deconfinement transition in this system, and can also be broken apart at low temperature by disorder. In the latter case, simulations show the system possesses properties reminiscent of a glassy state which qualitatively account for many of the experimental observations. |
| Friday, October 17, 2003 | Qaisar Shafi [Host: P. Q. Hung] | |
| 4:00 PM, Room 204 | Bartol Institute | |
| Physics Building | “Where does the Standard Model come from” |
| The Standard Model (SM) provides a highly successful description of strong, weak and electromagnetic interactions at present energies. In combination with Einstein's general relativity, it helps lay the foundation of another successful theory, the hot big bang cosmology. Some recent attempts to go beyond this theoretical framework will be discussed, necessitated in part by some exciting experimental discoveries, namely neutrino oscillations, existence of non-baryonic dark matter, CMB anisotropy,etc. |
| Friday, October 24, 2003 | Dr. Stuart A. Wolf [Host: Joe Poon and James Groves] | |
| 4:00 PM, Room 204 | University of Virginia, and DARPA at Arlington, VA | |
| Physics Building | “A new spin on electronics - spintronics” |
| Until very recently, the spin of the electron was ignored in mainstream electronics. The discovery of the giant magnetoresistance (GMR) effect in magnetic multilayers in 1988 and the subsequent development of sensors based on it began a transformation that will soon provide new paradigms for electronics for the new millenium. This talk will concentrate on the evolution of the DARPA spin electronics or spintronics project. The motivation, the science and the remarkable prospects for the future will be described in some detail. |
| Friday, November 7, 2003 | Paul Kwiat [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | U of Illinois, Urbana-Champaign | |
| Physics Building | “Entangled Photons for Quantum Information: 101 uses for a Schroedinger cat” |
| We have developed a means of producing entangled pairs of photons, using the process of spontaneous parametric downconversion in a novel two-crystal geometry. The quality of the source has enabled us to produce states of unparalleled purity, while the brightness has permitted an extreme violation of Bell's inequalities. Furthermore, the source is tunable, and we have been able to produce for the first time non-maximally entangled states, and states of arbitrary purity. The result is the capability to produce (almost) any two-photon quantum (polarization) state. Such states have application to such problems in quantum information as quantum cryptography, quantum teleportation, and quantum cooking. |
| Friday, November 14, 2003 | Peter Arnold [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “The BEC transition temperature of dilute gases: a not-so-simple problem in statistical mechanics” |
| The phase transition temperature for Bose-Einstein condensation of a three-dimensional ideal gas of bosons at fixed density is something that every physicist learns to calculate in graduate school, if not before. Amusingly, the first correction to that result, from arbitrarily weak interactions, is sufficiently challenging that only now is there beginning to appear some theoretical agreement on its magnitude, roughly 80 years after Einstein computed the ideal gas result. |
| Friday, November 21, 2003 | Collin Broholm [Host: Despina Louca] | |
| 4:00 PM, Room 204 | John Hopkins University | |
| Physics Building | “Quantum Coherence in Magnets” |
| Magnetic materials are typically found in one of two qualitatively different states: Thermally disordered at high temperatures or spin ordered at low temperatures. In this talk I describe a third distinct state of an interacting spin system: quantum ordered magnetism. I present neutron scattering data that provide evidence for quantum order in zero, one, two, and three-dimensional spin systems. La4Cu3MoO12 contains spin-trimers that develop quantum order at low temperature where each trimer becomes a composite spin-1/2 degree of freedom REFERENCES 1. Y. Qiu, C. Broholm, S. Ishiwata, M. Azuma, M. Takano, R. Bewley, and W. J. L. Buyers, cond-mat/0205018. 2. Guangyong Xu, J. F. DiTusa, T. Ito, H. Takagi, K. Oka, C. Broholm and G. Aeppli, Phys. Rev. B 54, R6827 (1996). 3. M. B. Stone, I. A. Zaliznyak, Daniel H. Reich, and C. Broholm, Phys. Rev. B 64, 144405 (2001). 4. M. B. Stone, J. Rittner, Y. Chen, H. Yardimci, D. H. Reich, C. Broholm, D. V. Ferraris, and T. Lectka, Phys. Rev. B 65, 064423 (2002). 5. M. Kenzelmann, G. Xu, I. A. Zaliznyak, C. Broholm, J. F. DiTusa, G. Aeppli, T. Ito, K. Oka, and H. Takagi. Phys. Rev. Lett. 90, 087202 (2003). 6. Y. Chen, Z. Honda, A. Zheludev, C. Broholm, K. Katsumata, and S. M. Shapiro Phys. Rev. Lett. 86, 1618 (2001). |
| Friday, December 5, 2003 | Luis Orozco [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | U. of Maryland | |
| Physics Building | “Conditional Dynamics and quantum feedback; an experiment in cavity QED” |
| Quantum systems that are strongly coupled have fluctuations that are larger than the average value of their steady state. When the fluctuation is a single photon, as is the case in cavity QED, the return to the steady state after the detection of a single photon follows conditional dynamics measurable with quantum optical correlations. The conditional dynamics can be modified, via quantum feedback, based on a single quantum and the knowledge of the conditional state. Work performed in collaboration with J. E. Reiner, W. P. Smith, M. L. Terraciano, and H. M. Wiseman with support from NSF and NIST of the USA. |
| Friday, January 16, 2004 | John Tranquada [Host: D. Louca] | |
| 4:00 PM, Room 204 | Brookhaven National Lab. | |
| Physics Building | “Superconductors of a Different Stripe: Charge Inhomogeneity and Superconductivity in Copper Oxides” |
| The standard model of electronic structure in solids is founded on the notion that electrons inevitably delocalize. In contrast, strong Coulomb repulsion in certain transition-metal oxide compounds can cause electron localization, resulting in the so-called "Mott-insulator" state. Cuprate superconductors consist of electronically-doped Mott insulators. Much of the continuing controversy over how to understand the cuprates concerns the issue of whether one can apply more or less conventional concepts of delocalized electrons, or whether radical new concepts are necessary. I will present experimental evidence, especially from neutron scattering, that the competition been kinetic and Coulomb energies leads to spatial inhomogeneities of charge carriers and antiferromagnetic correlations. It is possible that dynamic inhomogeneities are essential to achieving superconductivity at high temperature. |
| Friday, January 23, 2004 | Debbie Jin [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | Univ. of Colorado | |
| Physics Building | “Fun with Fermions: Exploring and Manipulating a Fermi Gas of Atoms” |
| Friday, January 30, 2004 | Nilanga Liyanage [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “Precision exploration of neutron spin structure at Jefferson Lab Hall A” |
| Spin structure functions provide basic information about the spin of the quark distributions inside the nucleon. Experimental understanding of the nucleon spin in the kinematic region where the three basic ("valence") quarks dominate the nucleon wave function is still rather poor. Jefferson lab, with its high quality, high polarization continuous electron beam and state of the art polarized nucleon targets in each of its three experimental halls is ideally suited for spin structure measurements in the valence region. An experimental program is underway at Jefferson Lab to measure the spin structure of the nucleon in the valence region with unprecedented precision. The planed upgrade of Jefferson lab CEBAF accelerator to 12 GeV will significantly increase the accessible kinematic range and the precision of these measurements. In this presentation I will give an overview of the neutron spin physics program at Jefferson Lab Hall A. I will also describe new experimental opportunities that will become possible in Hall A with the arrival of 12 GeV beam. |
| Friday, February 6, 2004 | Jongsoo Yoon [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “Superconductivity in 2-dimension” |
| Superconductivity occurring in 2-dimension has been understood in the framework of Kosterlitz-Thouless theory, and the nature of the transition is very different from that in 3-dimension. We present our recent data on superconducting properties of ultra-thin tantalum films, and compare with predictions based on the Kosterlitz-Thouless theory. Breakdown of superconductivity near the critical current and new findings on the phenomenon will also be discussed. |
| Friday, February 13, 2004 | Daniel J. Gauthier [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | Duke University - Fitzpatrick Center for Photonics and Communication Systems | |
| Physics Building | “Measuring the Information Velocity in Fast- and Slow-Light Media” |
| By all accounts, modern science and engineering has a very good understanding of how to use pulses of light to communicate information. It is, after all, the basis for one of the world's biggest and fastest-growing industries. And yet, the fundamental question of how fast information travels remains unanswered. The engineering community, starting with the seminal work by Shannon, has studied information rates, but has essentially ignored the question of the velocity of information. The physics community, initially prompted by an apparent challenge to Einstein's special theory of relativity, has been debating the issue off and on for almost 100 years. Surprisingly, the issue remains unresolved. There is no clear definition of the information velocity because there is only a vague understanding of where information is contained on a waveform. I will review the information velocity debate and present a technique for experimentally measuring the velocity of information for the case were the group velocity of a pulse of light vastly exceeds the speed of light in vacuum (a so-called "fast-light medium") or is much slower than the speed of light in vacuum (a "slow-light medium"). Our research suggests that the information velocity is equal to the speed of light in vacuum, independent of the characteristics of the medium. A tutorial on this topic, including links to recent publications, can be found at: By all accounts, modern science and engineering has a very good understanding of how to use pulses of light to communicate information. It is, after all, the basis for one of the world's biggest and fastest-growing industries. And yet, the fundamental question of how fast information travels remains unanswered. The engineering community, starting with the seminal work by Shannon, has studied information rates, but has essentially ignored the question of the velocity of information. The physics community, initially prompted by an apparent challenge to Einstein's special theory of relativity, has been debating the issue off and on for almost 100 years. Surprisingly, the issue remains unresolved. There is no clear definition of the information velocity because there is only a vague understanding of where information is contained on a waveform. I will review the information velocity debate and present a technique for experimentally measuring the velocity of information for the case were the group velocity of a pulse of light vastly exceeds the speed of light in vacuum (a so-called "fast-light medium") or is much slower than the speed of light in vacuum (a "slow-light medium"). Our research suggests that the information velocity is equal to the speed of light in vacuum, independent of the characteristics of the medium. A tutorial on this topic, including links to recent publications, can be found at: http://www.phy.duke.edu/research/photon/qelectron/proj/infv/ |
| Friday, February 20, 2004 | Cass Sackett [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “Atom Interferometry using Bose-Einstein condensates” |
| One of the chief applications envisioned for Bose-Einstein condensation is atom interferometry, in which the wave-like nature of a condensate is used to full advantage. A plethora of uses can be imagined, ranging from inertial sensing to probing surfaces. However, a variety of practical and fundamental obstacles must be overcome before condensate interferometry can be competitive with other techniques, even in a research setting. I will discuss our current understanding of these problems and some possible solutions, and report on progress in our experimental effort to build a condensate interferometer. |
| Friday, March 5, 2004 | John R. Tucker [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | Department of Electrical and Computer Engineering - University of Illinois at Urbana-Champaign | |
| Physics Building | “Quantum Computers and Atom-Scale Electronics in Silicon” |
| Over the past ten years, my colleague T.-C. Shen and I have developed a process for patterning individual phosphorous donors and self-ordered arrays into silicon with atomic resolution. This technique is now employed by the Australian Centre for Quantum Computer Technology and ourselves in efforts to build a silicon quantum computer. Our current research is focused on developing planar single-electron transistors to probe the quantum states of individual P donor 'qubits' inside the silicon crystal. Thus far, we have demonstrated electron wave interference across a 10nm-linewidth Aharanov-Bohm ring. Prospects for realizing a silicon quantum computer will be outlined, along with additional thoughts on future nanoelectronics and transport experiments. |
| Friday, March 19, 2004 | Dr. Kathleen Turner | |
| 4:00 PM, Room 204 | Dept of Energy, Office of Science, Office of High Energy Physics | |
| Physics Building | “High Energy Physics - On the Ground, Underground, and in Space” |
| The Office of High Energy Physics' mission is to explore the fundamental nature of matter, energy, space and time. The core of the program centers on investigations of elementary particles and the interactions between them using high energy particle accelerators. In order to fully explore the science, experiments are also done on the ground, underground and in space. The DOE HEP program provides about 90 percent of the federal support for high energy physics research in the U.S. and involves over 2,450 researchers at over 100 universities and 8 laboratories. The High Energy Physics current experimental program will be described, along with a look towards possibilities for the future. |
| Friday, April 2, 2004 | Ela Barbaris [Host: Bob Hirosky] | |
| 4:00 PM, Room 204 | Northeastern University | |
| Physics Building | “TBA” |
| Friday, April 16, 2004 | Seunghun Lee [Host: Joe Poon] | |
| 4:00 PM, Room 204 | National Institute of Standards and Technology | |
| Physics Building | “Unraveling the mysteries in complex oxides by neutron scattering” |
| Neutron scattering is one of the most powerful tools for studying magnetic and structural properties of solids. It has made seminal contributions in a wide range of fields in condensed matter physics and material science, from high Tc superconductivity, colossal magnetoresistance to quantum magnetism. In this talk, I will begin by introducing the basic principles of elastic and inelastic neutron scattering techniques. I will then describe a few exemplary neutron scattering results from high Tc superconductors and quantum magnets that were crucial to understanding the physics of these systems. |
| Friday, April 23, 2004 | Elliott Lieb [Host: E. Kolomeisky] | |
| 4:00 PM, Room 204 | Princeton University | |
| Physics Building | “The Dilute, Cold Bose Gas: A truly quantum-mechanical many-body problem” |
| The peculiar quantum-mechanical properties of the ground states of Bose gases that were predicted in the early days of quantum-mechanics have been verified experimentally relatively recently. The mathematical derivation of these properties from Schroedinger's equation have also been difficult, but progress has been made in the last few years (with R. Seiringer, J-P. Solovej and J. Yngvason) and this will be reviewed. For the low density gas with finite range interactions these properties include the leading order term in the ground state energy, the validity of the Gross-Pitaevskii description in traps, Bose-Einstein condensation and superfluidity in traps, and the transition from 3-dimensional behavior to 1-dimensional behavior as the cross-section of the trap decreases. The latter is a highly quantum-mechanical phenomenon. For the charged Bose gas at high density, the leading term in the energy found by Foldy in 1961 for the one-component gas and Dyson's conjecture of the N^{7/5} law for the two-component gas has also been verified. These results help justify Bogolubov's 1947 theory of pairing in Bose gases. |
| Friday, September 10, 2004 | Mark Whittle [Host: Peter Arnold] | |
| 4:00 PM, Room 204 | University of Virginia Astronomy | |
| Physics Building | “Primal Scream- Sounds From the Infant Universe” |
| Cosmology's extraordinary development shows no signs of slowing down. With the evolution of the Universe's average properties now fairly well understood, the focus has switched to the evoution of perturbations -- how an extremely smooth infant Universe changes into an extremely lumpy old Universe, with galaxies strewn to the horizon. Remarkably, the roots of present day structure can be traced back to sound waves in the early Universe. Even more remarkable, the power spectrum of the sound shows a fundamental and harmonics, as if the Universe were a kind of primitive musical instrument. This talk aims to unpack the relatively new subject of "Big Bang Acoustics", using reproductions of the primordial sound as a vehicle for discussing the physics of that remote time. It turns out that, as with many vibrating objects, the nature of the sound reveals much about the nature of the object as well as the nature of the stimulus. |
| Friday, September 24, 2004 | Milind Diwan [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Brookhaven National Lab | |
| Physics Building | “New Opportunities in Neutrino Oscillation Physics” |
| I will describe the remarkable new observations that have transformed our knowledge of the neutrino in the past few years. For over 70 years we knew very little about these particles becuase they are so difficult to detect. Now a new consistent picture has emerged about their basic properties. We can now ask new fundamental questions that might bridge the gap between our knowledge of the quarks and the leptons. |
| Friday, October 1, 2004 | Jane' Kondev [Host: Paul Fendley] | |
| 4:00 PM, Room 204 | Brandeis | |
| Physics Building | “The Physics of Confined DNA” |
| DNA in viruses and in cells is packed in spaces much smaller than its natural size. This state of confinement places interesting constraints on a variety of biological processes DNA is involved in, such as viral infection, gene expression, and recombination. Quantitative experimentation using techniques such as laser tweezers, cryo-electron microscopy and fluorescence spectroscopy has recently begun to probe in detail the confined state of DNA, both in living cells and in the test tube. In this talk I will describe this emerging experimental landscape and outline the theoretical challenges it poses. The particular examples I will focus on will be provided by DNA packing in viruses and gene regulation in bacteria. |
| Friday, October 8, 2004 | Professor Shmuel Nussinov [Host: P.Q. Hung] | |
| 4:00 PM, Room 204 | Tel Aviv University | |
| Physics Building | “A Physicist Approach to Complex Problems” |
| Friday, October 15, 2004 | Thomas Cohen [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | University of Maryland | |
| Physics Building | “The Science and Sociology of Pentaquarks” |
| Friday, October 22, 2004 | Joel Moore [Host: Paul Fendley] | |
| 4:00 PM, Room 204 | Berkeley | |
| Physics Building | “Hidden Dimensionality in Frustrated Magnets and Complex Superconductors” |
| The idea that the true dimensionality of a system may differ from its superficial dimensionality appears in many areas of modern theoretical physics. A central theme of recent research in correlated electrons is that two- and three-dimensional materials can, in some cases, show exotic physics familiar from one spatial dimension. Quantum phenomena typically restricted to one dimension, like exact self-duality and a vortex-mediated (Kosterlitz-Thouless) phase transition, can appear in dimensions d>=2 as well. We discuss specific examples of this "dimensional reduction" that are based upon four-spin interactions generated in frustrated magnets and in effective descriptions of some superconductors. |
| Friday, October 29, 2004 | Frank Moss [Host: Acar Isin] | |
| 4:00 PM, Room 204 | University of Missouri St. Louis | |
| Physics Building | “Random Walks with a Zooplankton” |
| Theories of swarming and pattern formation have recently become of interest to engineers, chemists and physicists. Interesting examples are offered by various self-propelled biological agents both in simulations and in reality. But well-defined swarming experiments in the lab using real biological agents have been problematic up to now due to size limitations of the animal groups or lack of precise knowledge of the agent-agent or agent-medium interactions. We present the results of lab experiments with the zooplankton /Daphnia/, or “water flea” intermediate in size and complexity between bacteria and birds or fish, for example. Our experiments are compared to predictions of the “Active Brownian Particle” theory developed by a group at Humboldt University in Berlin. /Daphnia/ show the entire range of the theoretically predicted behaviors from single agent to collective motions of swarms and can be observed to perform a fascinating bio-hydrodynamic vortex under certain conditions. |
| Friday, November 19, 2004 | Alan Dorsey [Host: Michael Fowler] | |
| 4:00 PM, Room 204 | University of Florida | |
| Physics Building | “Electronic Liquid Crystals: Novel Phases of Electrons in Two Dimensions” |
| There is growing experimental evidence that electrons confined to two dimensions (in a semiconductor heterostructure, for instance) at low temperatures and high magnetic fields can display a plethora of partially ordered phases which have the same symmetries as classical liquid crystal phases, such as nematics and smectics. I will review the experimental evidence for these novel quantum phases of matter, discuss several analogous classical systems, and motivate some of the theoretical models for these "quantum Hall liquid crystals". |
| Friday, December 3, 2004 | Alessandro Drago [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | Universita' degli Studi di Ferrara | |
| Physics Building | “Gravitational Waves as a Tool to Investigate Neutron Star Structure” |
| The new generation of Gravitational Wave detectors, including in particular Laser Interferometers as LIGO, is now becoming fully operative. This will offer the possibility to confirm the existence of the waves predicted by General Relativity and it will also provide the nuclear and astrophysics communities with a new tool to investigate the inner structure of compact stellar objects. |
| Friday, January 21, 2005 | C. L. (Lew) Cocke [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | Kansas State University | |
| Physics Building | “Photon-ion Collisions and Molecular Clocks” |
| The timing of molecular rearrangemnts can be followed in the time domain on a femtosecond scale by using momentum imaging techniques. Three examples will be discussed: First, the diffraction of electrons ejected from the k-shell of one of atomic constituents of the molecule takes a "picture" of the molecule, and the correlation between the momentum vector of the photoelectron and the subsequent fragmentation pattern is used to estimate the time delay which accompanies the latter process. Second, the kinetic energy release of proton pairs from the double ionizaton of hydrogen by fast laser pulses is timed using the 2.7 fs optical cycle as a clock. The mechanisms of rescattering, sequential and enhanced ionization are clearly identified in the momentum spectra. Pump probe experiments allow us to follow the simultaneous propagation of coherently launched wave packets in different exit channels. Third, the operation of rescattering double ionization in the case of nitrogen and oxygen molecules will be discussed. The use of rescattering to probe the structure of the outer orbitals in molecules will be demonstrated. |
| Friday, February 4, 2005 | Lawrence Krauss [Host: P.Q. Hung] | |
| 4:00 PM, Room 203 | Case Western Reserve University | |
| Physics Building | “Life, the Universe, and Nothing: The Future of Life in an Ever-Expanding Universe” |
| In this talk, I will ruminate on the future of the Universe itself, and also on the future of life within it, using as my starting point recent observations in cosmology. I will first discuss why the Universe we appear to inhabit is the worst of all possible universes, as far as considerations of the quality and quantity of life is concerned. Then, I will describe how fundamental aspects of the way in which we teach cosmology, in particular the relation between geometry and destiny, has been forever altered by recent discoveries. Finally, I will address the fascinating question of whether life might be eternal in an eternally expanding universe. The answer to this question appears to hinge on issues of basic physics, in particular on issues of quantum mechanics and computation, which may determine whether life is ultimately analogue or digital. |
| Friday, February 11, 2005 | Rich Superfine [Host: Keith Williams] | |
| 4:00 PM, Room 204 | University of North Carolina | |
| Physics Building | “NANOMACHINES: From Atomic Lattice Gears to Cystic Fibrosis” |
| The promise of nanotechnology will be realized through the interplay of new tools and the appreciation of the lessons from biological systems. The challenge of nanomachines ranges from the understanding of the interactions between atomic scale systems to the harnessing of the force generation capabilities of biological systems. We are developing a suite of tools for nanoscale science including the combination of force measurement and manipulation systems in conjunction with scanning probe, electron and optical microscopy. For the basic elements of nanomachines, we have studied gears, springs and electrical contacts of carbon nanotubes. Through the study of carbon nanotube dynamics we have observed that atomic lattices can act like gears in promoting the rolling of nanotubes. Most recently, we have begun a study of nanotubes as torsional springs, have measured the torsional spring constants in freely suspended paddles and have observed strain hardening in individual nanotubes. Finally, biology has developed its own nanomachines and microfluidic systems that include beating cilia to produce flow and complex closed loop feedback mechanisms. We have begun to study this system within a cell culture using a new 3D manipulation system, and will discuss our early results in quantifying the forces applied by beating cilia and studies of the resulting flow. |
| Friday, February 18, 2005 | Rusi P. Taleyarkhan [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | The Purdue University | |
| Physics Building | “Acoustic Inertial Confinement Nuclear Fusion - Status and Challenges” |
| Energetic bubble implosions can generate sonoluminescence (SL) light flashes along with extreme states of compression and temperatures. In cavitation experiments with chilled deuterated acetone, neutron and tritium nuclear emissions were detected, indicative of thermonuclear fusion. The neutron emissions were time correlated with SL light emission. The gamma ray emissions were delayed as would be expected from neutron slowing down and capture. Control experiments with normal acetone did not result in tritium activity or neutron emissions. Fusion was observed during experiments in which the nanoscale nucleation of bubbles was induced in chilled deuterated acetone using a pulse neutron generator as well as with an isotope neutron source. Video images clearly indicate the existing of complex bubble clusters when bubble fusion occurs, and also the formation of comet-like structures which were detrimental to bubble nuclear fusion. Hydrodynamic shock code simulations have supported the experimental findings and indicate temperatures during implosion in the 108K range along with Gbar shock pressures in the imploding bubbles within bubble clusters, but not in single bubble environments. Recent results of experiments will be presented along with discussions related to key technical challenges concerning modeling and experimentation. |
| Friday, March 25, 2005 | E. Paschos [Host: Brad Cox] | |
| 4:00 PM, Room 204 | University of Dortmund, Germany | |
| Physics Building | “Planetary Models From the Middle Ages” |
| A small and compact article from AD 1300 describes models for the planets and the moon. It proposes epicyclic theories which deviate from Ptolemy' s Almagest. The Colloquium reviews the models and their accuracy . Then compares them with Arabic models of that time as well as the Newtonian theory. It also demonstrates how scientific knowledge was preserved in the Middle Ages and was transmitted to Italy to spark the beginning of the Copernican Rovolution. |
| Friday, April 1, 2005 | J. E. Thomas [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | Duke University | |
| Physics Building | “High-Temperature Superfluidity in Ultra-Cold Fermi Gases” |
| An optically-trapped Fermi gas of 6Li atoms becomes strongly interacting when it is tuned to a Feshbach scattering resonance. Such a gas is predicted to be a very high temperature superfluid - the transition temperature is a large fraction of the Fermi energy. I will describe experimental evidence for superfluidity which arises in anisotropic expansion of the gas, in the heat capacity, and in collective damping. These cold Fermi gases provide desktop analogs of exotic, strongly-interacting fermions in nature, from high temperature superconductors and neutron stars to quark-gluon plasmas. |
|
Thursday, April 7, 2005 Note Special Day |
AVAILABLE | |
| 4:00 PM, Room 204 | TO BE ANNOUNCED | |
| Physics Building | “TO BE ANNOUNCED” |
| Friday, April 8, 2005 | Al Shapere [Host: Paul Fendley] | |
| 4:00 PM, Room 204 | University of Kentucky | |
| Physics Building | “Production of Microscopic Black Holes by Cosmic Rays” |
| Cosmic ray events may create black holes if extra dimensions exist and are sufficiently large. In particular, neutrino cosmic rays may produce black holes deep in the atmosphere, initiating characteristic quasi-horizontal showers far above the standard model rate. The fact that no such showers have been observed to date places an upper bound on the size of these extra dimensions. Continued nonobservation of such events over the next few years would improve these bounds significantly, and sharply limit the rate of black hole production at LHC. On the other hand, if black hole mediated showers are observed in the next few years, they could provide the first experimental evidence for extra dimensions, string theory, and the formation and decay of microscopic black holes. |
| Friday, April 15, 2005 | Marco Mirazita [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | INFN, Laboratori Nazionali di Frascati | |
| Physics Building | “The Search For the Exotic 5 Quark Baryons” |
| All the well established particles can be classified using the constituent quark model as quark-antiquark states for mesons and 3-quarks states for baryons. However, QCD does not forbid the existence of more complicated internal structures. All the states with quark content different than quark-antiquark or 3-quarks are called "exotic". Exotic particles have been searched for many year in the past, but no positive results have been find until 2003, when several experimental groups reported the first evidences (even if with low statistical significance) for an exotic pentaquark state, the Theta+(1540). On the other hand, several other experiments did not find positive evidence for this state, thus suggesting that, if the Theta+ exists, it should be a really exotic particle. After these first experimental results, several laboratories planned new high-statistic experiments, such those performed and presently under analysis at Jefferson Laboratory. The aim of these experiments is first of all to confirm the existence of Theta+(1540), then to set in an unanmbiguous way its properties. In this talk, a review of the experimental situation will be given, and what we need to conclude that the first exotic baryon has been discovered will be discussed. |
| Friday, April 22, 2005 | Klaus Hon [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Ohio State University | |
| Physics Building | “The Asymmetry Between Matter and Anti Matter - or -How to Know if it is Safe to Shake an Alien's Hand?” |
| Most of us have looked at the spectacular pictures taken by the Hubble Space Telescope. Galaxies, nebulae, super novae -- but there is something peculiar about these images. Where ever we look in space we only see matter. No significant quantities of anti-matter have been found. Since we believe equal amounts of matter and anti-matter have been produced originally we must conclude that there is an asymmetry between particle and anti-particle decays. In the laboratory, however, nature always seems to obey the particle - antiparticle symmetry with one known exception. Almost 40 years ago a small difference has been found in the neutral kaon system. But the nature of this system made it extremely difficult for both theorists and experimentalists to extract a clear picture of this effect. For years there has been great hope in the particle physics community that a large matter - antimatter asymmetry can be observed in a new system - the weak decays of massive B mesons. The past decade has seen a vigorous experimental effort to produce the large quantities of B mesons required to discover the cause of this asymmetry. Particle accelerators have been upgraded and new detectors were constructed. As we enter the Golden Age of B physics nearly a billion B meson decays have been recorded by these experiments. I will review some of the old questions that have been answered and discuss some of the new puzzles that have been uncovered. |
| Friday, April 29, 2005 | Marina Artuso [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Syracuse | |
| Physics Building | “In Search of New Physics: The Clues From Charm” |
| The study of the interactions between the fundamental building blocks of matter is a critical component of our understanding of the history of the universe and its dynamics. My talk will describe how our experimental study of charm quark decays may test key features of our present understanding of these interactions, and, possibly, open a window towards new physics. The experimental data discussed are taken at the CESR electron-positron collider. |
| Friday, May 6, 2005 | Sankar Das Sarma [Host: Keith Williams] | |
| 4:00 PM, Room 204 | University of MarylandCondensed Matter Theory Center - | |
| Physics Building | “Tidbits About Qubits: Spin Computation in Nanostructures” |
| I will provide an introduction to the emerging field of spintronics and spin qubits in this talk. Active control of carrier spin in nanostructures of semiconductors and other electronic materials is projected to lead to new device functionalities in the future. In particular, it may be possible to envision memory and logic operations being carried out on the same 'spintronic' chip. I will discuss various aspects of fundamental physics related to this new research area of spin electronics with the particular emphasis on localized electron spins in semiconductor nanostructures, such as GaAs quantum dots and P donors in Si. A revolutionary possibility in the (perhaps, far) future is using the natural two-level quantum dynamics of electron spin to create robust quantum bits ('qubits') which could be used to carry out solid state quantum information processing or quantum computation. I will discuss in details the questions of entanglement, decoherence, quantum error correction, and quantum gates in semiconductor nanostructure-based solid state spin quantum computer architectures, critically discussing from a theoretical perspective the current status of the field and the prospects for carrying out large-scale quantum computation using solid state spin qubits. Aspects of fundamental spin physics in the solid state environment will be emphasized in this talk. This research has been supported by LPS, ARDA, NSA, ARO, DARPA, ONR, and Please see http://www.physics.umd.edu/cmtc for the relevant publications. |
|
Tuesday, May 31, 2005 Note Special Day |
Professor Theodor Hansch [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | Max Planck Institute for Quantum Optics | |
| Physics Building | “Towards a Quantum Laboratory on a Chip” |
| Friday, August 26, 2005 | AVAILABLE | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, September 2, 2005 | AVAILABLE | |
| 4:00 PM, Room 204 | ||
| Physics Building |
|
Thursday, September 8, 2005 Note Special Day |
Thom Mason [Host: Seunghun Lee] | |
| 4:00 PM, Room 204 | Director, Spallation Neutron Source - Oak Ridge National Laboratory | |
| Physics Building | “The Spallation Neutron Source: A Powerful Tool for Materials Research” |
| The wavelengths and energies of thermal and cold neutrons are ideally matched to the length and energy scales in the materials that underpin technologies of the present and future: ranging from semiconductors to magnetic devices, composites to biomaterials and polymers. The Spallation Neutron Source will use an accelerator to produce the most intense beams of neutrons in the world when it is complete in 2006. The project is being built by a collaboration of six U.S. Department of Energy laboratories. It will serve a diverse community of users drawn from academia, industry, and government labs with interests in condensed matter physics, chemistry, engineering materials, biology, and beyond. |
| Friday, September 9, 2005 | Doug Osheroff [Host: Craig Dukes] | |
| 4:00 PM, Room 203 | Stanford University | |
| Physics Building | “Understanding The Columbia Shuttle Accident and NASA's Challenges Posed by Discovery” |
| On 1 February 2003 space shuttle Columbia broke up during re-entry over the plains of East Texas. The speaker was a member of the board appointed to investigate that disaster. It was ultimately found that the physical cause of the accident was a piece of thermally insulating foam that struck the leading edge of the left wing during launch. This foam had a density of just 1/30th the density of water, yet it created a hole estimated to be approximately 25 cm square, which allowed superheated gases to enter the wing on re-entry, consuming the interior of the wing in a matter of a few minutes. The final report showed that NASA had that such foam strikes had occurred before, but continued to fly in the face of clear and persistent danger. The speaker will also discus the organizational aspects of this accident, many of which are common to all large organizations, and the future of the program in light of Discovery's foam shedding. |
| Friday, September 16, 2005 | Chris Morris [Host: Craig Dukes] | |
| 4:00 PM, Room 204 | Los Alamos National Laboratory | |
| Physics Building | “Charge Particle Radiography for National Security” |
| Intermediate energy protons are being used for very fast (flash) radiography. Proton beams have shown to provide a flexible time format, excellent position resolution, and adjustable contrast, for a wide range of high explosive driven experiments. These experiments are playing an increasingly important role in the nuclear stockpile stewardship program. An outgrowth of this work has been the development of cosmic ray radiography for cargo and vehicle inspection. An overview of charge particle radiography and its uses for national security applications will be presented. |
| Friday, September 23, 2005 | William Klemperer [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | Harvard University | |
| Physics Building | “The Chemistry of the Universe” |
| Friday, September 30, 2005 | Mordechai Feingold [Host: Michael Fowler] | |
| 4:00 PM, Room 203 | Caltech | |
| Physics Building | “All Was Light: Isaac Newton's Revolutions” |
| Friday, October 7, 2005 | Sarah Eno [Host: Bob Hirosky] | |
| 4:00 PM, Room 204 | University of Maryland | |
| Physics Building | “The CMS Experiment” |
| Friday, October 21, 2005 | Gary Goldstein [Host: Simonetta Liuti ] | |
| 4:00 PM, Room 204 | Tufts University | |
| Physics Building | “The Importance of Spin in Particle Physics” |
| Friday, October 28, 2005 | Catherine Brechnigac [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | ||
| Physics Building | “Clusters: a route to study stability at nanometer scale” |
| Friday, November 4, 2005 | Peter Olson [Host: Keith Williams] | |
| 4:00 PM, Room 204 | John Hopkins University - Earth and Planetary Sciences | |
| Physics Building | “Probing the Geodynamo” |
| Friday, November 11, 2005 | Jeremy Levy [Host: Joe Poon] | |
| 4:00 PM, Room 204 | University of Pittsburgh | |
| Physics Building | “Oxide-Semiconductor Materials for Quantum Computation” |
| Quantum computers, as yet undeveloped, are believed to be able to efficiently solve strategically important problems like number factorization, database search, and the Schrodinger equation itself. The staggering potential of these and other applications has led to a worldwide race to build the first working quantum computer. The state of experimental quantum computation is primitive--neither quantum bits (qubits) nor quantum gates (qugates) have been demonstrated in a scalable form. In this talk, I will give an overview of the new field of quantum information science and technology, and will describe a proposal to create a quantum information processor using ferroelectrically coupled electron spins in silicon. This approach combines the latest advances in nanostructure and heterostructure design, ultrafast optical control, measurement science and signal processing. Progress toward these goals, pursued within the Center for Oxide-Semiconductor Materials for Quantum Computation (COSMQC), will be described. This work is supported by DARPA QuIST through ARO contract number DAAD-19-01-1-0650. |
| Friday, November 18, 2005 | Joe Poon [Host: Genya Kolomeisky] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “Glassy Metals – Complexity Made Simpler ” |
| Although ubiquitous in nature and technology, the microscopic study of liquids and glasses lags far behind that of crystals and quasicrystals. This is because liquids and glasses do not exhibit long-range order, which frustrates theoretical description. To date, the common approaches for modeling the dynamics and glass transition of liquids are based on the potential energy landscape paradigm. Theoretical approaches such as the mode-coupling theory and replica method, although successful in advancing our understanding of the dynamics and thermodynamics of the liquid-glass transition, have not provided specific predictions of the important parameters of the glassy state. Recently, a simple complementary model based on atomic-level fluctuations in the amorphous network has been successfully applied to the computation of these parameters. The latter approach may also provide a pathway to a more general microscopic understanding of liquids and glasses. The rest of this talk will focus on glassy metals as futuristic metals with certain promising and enabling properties. |
| Friday, November 25, 2005 | ****THANKSGIVING BREAK**** | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, December 2, 2005 | Roger Rusach [Host: Brad Cox] | |
| 4:00 PM, Room 204 | University of Minnesota | |
| Physics Building | “Physics and the CMS Detector at the CERN Large Hadron Collider” |
| In 2007 a new proton-proton collider, the LHC, will turn on and a whole new energy domain will become accessible to experiment. Indications of what we might observe come from current measurements in experiments in high-energy physics, astrophysics and cosmology. We will discuss what problems in physics might be resolved with data from the LHC, describe how the detectors work and what are the special challenges associated with building a detector of the scale required for this energy region. |
| Friday, January 20, 2006 | Art Brill [Host: Genya Kolomeisky] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “Nuclear Spin-Electron Spin Interactions in the Three-Atom System H2N” |
| H2N has one unpaired electron and three nuclei of non-zero spin. The four H2N isotopes from 1H, 2H, 14N and 15N have corresponding sets of hyperfine interactions. Measurements of these constrain calculations of electronic wavefunctions and energies, and provide basic knowledge for application to more complex systems. Nuclear spin-state mixing arises from the off-diagonal elements of the nuclear energy matrix, e.g. Mxx ≡ σκ 〈ψ|Σ (Skzx2kn/r5kn + Sk'zx2k'n/r5k'n|Ψ〉 (Airne and Brill, Phys. Rev.A 63 052511). The principle hyperfine A-values can be expressed in terms of the M’s, e.g. Azz = AFermi - (4/3σ)( Mxx + Myy - 2 Mzz), thereby simplifying the energy matrices. In the absence of nuclear spin-state mixing (i.e. each state pure mI) there are, e.g. 10 epr transitions in D215N and 15 in D214N, all ΔmI = 0 fully allowed. In the presence of mixing there are 243 in D215N and 729 in D214N, with large differences in probability among transitions. Because of numerous, at least partially allowed, overlapping transitions, useful information can be obscured in H2N magnetic resonance spectra. Research is required to arrive at effective experimental conditions. The wide range of transition probabilities will cause H2N resonances to exhibit a corresponding range of microwave power saturation behavior. Simulations display remarkable effects which call for experimental verification by employing a wide range of powers. The nuclear Zeeman interaction (proportional to B) perturbs both the energy and state mixing of nuclear levels, thereby affecting the separation and probability of resonances. Of special interest are the fields Bcross at which pairs of hyperfine levels draw closest. A spectrometer with microwave frequency scanning at fixed B would be useful for centers like H2N in which on-diagonal hyperfine energy matrix elements depend significantly upon B. |
| Friday, February 3, 2006 | Gail McLaughlin [Host: Steve Thornton] | |
| 4:00 PM, Room 204 | North Carolina State University | |
| Physics Building | “Exploding Stars, Neutrinos, and Nucleosynthesis” |
| The subject of supernovae is a unique combination of many different branches of physics and there are different ways in which we can probe the inner workings of these objects. Beyond examining light curves from the explosion, one can study nucleosynthesis products and neutrino spectra. The discovery of a whole new type of supernova, one which creates a gamma ray burst, has created a new frontier in research on neutrinos and element synthesis. I will discuss the role neutrinos play in determining whether the heaviest elements, such as uranium and thorium, are produced in these environments. |
| Friday, February 17, 2006 | Christopher Stubbs [Host: Brad Cox] | |
| 4:00 PM, Room 203 | Harvard University | |
| Physics Building | “Preliminary Results on the Nature of the Dark Energy from the ESSENCE Supernova Survey ” |
| The discovery of the accelerating expansion of the Universe provides clear evidence of physics beyond the standard model. Our current challenge is figuring out what it means! I will describe the initial results we have obtained in the ESSENCE supernova survey. This project was designed to detect 200 type Ia supernovae in the redshift range between 0.2 < z < 0.8, with the goal of measuring the equation of state parameter of the Dark Energy. We are paying particular attention to potential sources of systematic errors that might afflict the measurement, and I will describe some of the steps we are taking to both control and quantify these effects. |
| Friday, February 24, 2006 | Linda Horton [Host: Despina Louca] | |
| 4:00 PM, Room 204 | ORNL | |
| Physics Building | “The Center for Nanophase Materials Sciences” |
| The Center for Nanophase Materials Sciences is the newest user facility at Oak Ridge National Laboratory. Located adjacent to the Spallation Neutron Source, the CNMS is one of 5 nanoscience user facilities being built by the Department of Energy. CNMS is open to scientists and engineers for research to understand the phenomena that control the properties of nanoscale materials. CNMS emphasizes synthesis and characterization, including neutron scattering and electron microscopy. One important capability is a 10,000 sq ft nanofabrication clean room facility. CNMS will also integrate theory and modeling with the experimental program, a critical aspect of the research. The presentation will discuss the capabilities of the new facility, the scientific program, and opportunities for research and collaboration. |
| Friday, March 3, 2006 | RESERVED [Host: JKG] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “TBA” |
| Friday, March 10, 2006 | ****SPRING RECESS***** | |
| 4:00 PM, Room 204 | ||
| Physics Building |
|
Thursday, March 16, 2006 Note Special Day |
David Weiss [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | Penn State University | |
| Physics Building |
| Friday, March 17, 2006 | Ralph McNutt [Host: Blaine Norum] | |
| 4:00 PM, Room 204 | Johns Hopkins University | |
| Physics Building | “The MESSENGER Mission to Mercury: Science and Status” |
| Friday, March 24, 2006 | Sally Dawson [Host: P.Q. Hung] | |
| 4:00 PM, Room 204 | Brookhaven National Laboratory | |
| Physics Building | “Adventures at the Terascale” |
| Exciting opportunities are in store for particle physics over the coming decade, with new tools and experiments poised to explore the frontiers of high energy, the smallest distance scales, and processes of great rarity. Einstein's dream of a unification of all forces will be tested at new energy scales and with greater precision than ever before. The Large Hadron Collider at CERN will begin the exploration of higher energy scales than have been tested previously and a possible future high energy lepton collider will continue our explorations. |
| Friday, March 31, 2006 | Tom Ferbel [Host: Bob Hirosky] | |
| 4:00 PM, Room 204 | DOE/University of Rochester | |
| Physics Building | “Whither Particle Physics” |
| Friday, April 7, 2006 | Oscar Rondon-Aramayo [Host: Genya Kolomeisky] | |
| 4:00 PM, Room 204 | UVA | |
| Physics Building | “Nucleon Structure Studies with Polarized Photons and Polarized Nucleons” |
| The quark and gluon structure of the nucleons (protons and neutrons) was established by illuminating atomic nuclei with high energy unpolarized real and virtual photons. The interactions between quarks follow "scaling" rules that were also established with unpolarized photons. With polarized photons it is possible to explore the nucleon structure even further. Polarized photons have been used to determine that quarks carry only 1/3 of the spin, but the distribution of spin among types ("flavors") of quarks is still under study. And the "missing" spin carriers are still being investigated. The interactions between quarks and gluons have barely been explored experimentally. Polarized photons can also uncover the details of those interactions and relate them to calculations based on Quantum Chromodynamics - QCD, the fundamental theory of strong interactions. There is an extensive program of nucleon structure studies with polarized photons and polarized nuclear targets at Jefferson Lab with the goal of answering some of these and other related questions. Highlights of the Hall C component of this program will be presented. |
| Friday, April 14, 2006 | Yuri Gershtein [Host: Bob Hirosky] | |
| 4:00 PM, Room 204 | Florida State University | |
| Physics Building | “News from the Energy Frontier” |
| It is exciting time for particle physics. Currently, Fermilab's Tevatron, the highest energy accelerator, delivered more than 1 fb-1 to the experiments (CDF and DZero). In just over a year, the Large Hadron Collider (LHC) at CERN will turn on, moving the energy frontier by almost an order of magnitude - an event the likes of which we did not see in almost three decades. I will talk about the fundamental questions that are addressed by doing physics at the energy frontier, present some new results from DZero experiment and describe the status and prospects of the CMS detector at the LHC. |
| Friday, April 21, 2006 | Peter Shanahan [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Fermi National Accelerator Laboratory | |
| Physics Building | “Recent Results and Future Prospects in Neutrino Physics” |
| More than 40 years ago, a Nobel Prize winning experiment showed that neutrinos come in distinct flavors: neutrinos created in association with muons produced only muons when they interacted, and not electrons. Over the past decade, however, a series of experiments have established that the flavor of a neutrino does indeed change with time. The most likely explanation of this phenomenon is neutrino flavor oscillation, requiring a finite neutrino mass and therefore an extension of the Standard Model of Particle Physics. Related physics at energies far beyond direct experimental reach may well explain the preponderance of matter over antimatter in the universe. The impact of accelerator-based experiments in our understanding of neutrino masses and flavor will be discussed, with an emphasis on current and anticipated experiments at Fermilab. |
|
Tuesday, April 25, 2006 Note Special Day |
Xiaodong Jiang [Host: Nilanga Liyanage] | |
|
3:30 PM, Room 204 Note Special Time |
Rutgers University | |
| Physics Building | “Can Quarks in a Polarized Nucleon Tell Left from Right ?” |
| In the strong interaction, which follows the parity-conserving theory of Quantum Chromodynamics (QCD), can quarks in a polarized nucleon manage to tell left from right ? For "collinear quarks" in a longitudinally polarized nucleon, the answer is simply NO. However, when a nucleon's spin is oriented transverse to it's momentum, quarks inside can figure out left from right through their transverse spin distributions (transversity) and through their angular motions. Recent spin physics experiments from HERMES at DESY and COMPASS at CERN have revealed such an amazing behavior of quarks for the first time, left us with even more questions. Two upcoming Jefferson Lab experiments are designed to provide more answers as to how exactly u- and d-quarks tell left from right in a transversely polarized nucleon. |
| Friday, April 28, 2006 | Paul C. Canfield [Host: Seung-Hun Lee] | |
| 4:00 PM, Room 204 | Ames Laboratory and Department of Physics and Astronomy, Iowa State University | |
| Physics Building | “The Design, Growth, Discovery and Characterization of Novel Intermetallic Compounds” |
| In this talk I will review the motivations as well as means for the design, growth or search for novel materials. I will provide examples of what physics you can peruse ranging from superconductivity in MgB2, to the spin-glass state in rare earth based quasicrystals, to field induced quantum criticality in Yb-based intermetallics. The emphasis will be on the joy of, and tools for, discovery. |
|
Monday, May 1, 2006 Note Special Day |
Kent Paschke [Host: Nilanga Liyanage] | |
|
3:30 PM, Room 204 Note Special Time |
University of Massachusetts | |
| Physics Building | “Using Parity Violation to Probe Strange Quarks in the Nucleon” |
| The basic nuclear building block of our day-to-day world, the nucleon, is well described in terms of quarks of only two varieties: the up and down quarks. However, the nucleon is more complex than the apparent success of the constituent quark model would imply. One example of this complexity is the possible role of the strange quark in the nucleon. Precision measurements of parity violation in electron scattering, a symmetry violation which is forbidden under the electromagnetic interaction but allowed by the weak force, can be used to disentangle the contributions of strange quarks from other components of the nucleon electric and magnetic structure. I will report new results on the most precise measurement to date of parity-violation in electron-nucleon scattering, from the HAPPEX collaboration at Thomas Jefferson National Accelerator Facility, and discuss implications for the question of strange quarks in the nucleon. |
|
Thursday, May 4, 2006 Note Special Day |
Xiaochao Zheng [Host: Nilanga Liyanage] | |
|
3:00 PM, Room 205 Note Special Time |
MIT | |
| Physics Building | “What Have We Learned from Polarized Deep Inelastic Scattering?” |
| Since the 1980's development in polarized electron sources and polarized target techniques has brought the experimental study of the nucleon into a new era: The spin structure of the nucleon has been explored with polarized electron scattering. Now twenty years have passed. What have we
learned from the data? Do they agree with predictions from quantum chromo-dynamics (QCD), the theory for strong interactions? And what about
predictions from constituent quark models? I will start from an introduction to the study of hadron structure using lepton deep inelastic scattering and give an overview of world data and what we have already learned about nucleon structure. Then I will present results from a precision experiment completed at Jefferson Lab on the neutron spin in the valence quark region, and discuss about the future of this measurement. The last 10 minutes of the talk will be devoted to a different topic: using polarized electron scattering to test the electro-weak Standard Model and hadronic structure, and introducing the PV-DIS program that is being just launched at Jefferson Lab. The talk will be given on an non-expert level. |
|
Tuesday, May 9, 2006 Note Special Day |
Daniela C. Rohe [Host: Nilanga Liyanage] | |
|
3:30 PM, Room 204 Note Special Time |
University of Basel, Switzerland | |
| Physics Building | “Experiments With Polarized 3He at the Mainz Microtron (MAMI)” |
| Polarized 3He is an interesting target for nuclear physics experiments due to its particular spin structure which allows its use as a polarized neutron as well as polarized proton target. Further, the nucleus is simple enough that exact solutions of its wave function and the reaction channels are available. On the other hand all important interactions between the three nucleons are present and can be studied. Polarization experiments open up new degrees of freedom and find a wide field of application due to their particular sensitivity as well as due to the advantages of asymmetry measurements in general. In this talk I will discuss polarized target technology and will explain the technique and installation used to polarize 3He for the nuclear physics target at MAMI. The emphasis of the talk is on the results achieved so far at MAMI with polarized 3He. Their purpose is twofold: To test the reliability of the theoretical description of 3He and to measure the electric form factor of the neutron. An outlook about ongoing and future research will be given. |
| Friday, September 8, 2006 | Vittorio Celli [Host: Steve Thornton] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “The Ocean Tides: Myth and Truth from Galileo to GPS” |
| It is widely believed, and taught in Physics courses, that two high tides of equal magnitude occur daily. In reality, the tides are a complicated sloshing of the oceans with three main periods: M2 (12.82h) due to the Moon, S2 (12h) due to the Sun, and K1 (23.93h) due to both and to the tilt of the Earth's axis. Following Newton, one can compute the magnitude of the tidal forces, but an understanding of tide dynamics, based on the work of Laplace and Lord Kelvin, is incomplete even today. Over most coastlines M2 is dominant, but in New Orleans, for instance, there is only one high tide each day. In the North Atlantic, the M2 tide runs up the European coast and down the American coast, circling a mid-Ocean point of zero amplitude. This "amphidromic" behavior is seen in many basins, and is due to the Coriolis force acting on tidal currents. Thus, the ocean tides are a direct proof of the Earth's rotation, as Galileo maintained. In fact, his kinematic theory of the "ebb and flow of the waters", based on the Copernican motions of Earth, Sun and Moon, is basically correct, although incomplete. An accurate global picture of tidal amplitudes (but not yet of tidal currents) has been obtained by GPS satellites, and is in turn relevant to space age science and technology. |
| Friday, September 15, 2006 | Brooks Harris [Host: Seunghun Lee] | |
| 4:00 PM, Room 204 | University of Pennsylvania | |
| Physics Building | “The Unusual Symmetry of Ferroelectricity in Incommensurate Magnets” |
| The coupling between electric and magnetic properties in condensed matter systems is usually very weak. In part this may be viewed as being a result of the fact that the electric and magnetic fields exhibit different symmetries which do not naturally couple to one another. Here I discuss a class of materials which display a very unusual phase transition in which magnetic ordering and the development of ferroelectricity occur simultaneously. This coupling has drawn great interest recently mainly due to various experimental results for this fascinating coupling whereby magnetic ordering induces erroelectricity. My main objective is to understand the phenomonology of this magnetoelectric coupling via a Landau expansion whose consequences depend crucially on the symmetry properties of the magnetic order and the consistency of this order with ferroelectric ordering. Even this simple phenomenological theory explains a number of nontrivial ferroelectric properties which have been observed. I discuss briefly the advantages of such a symmetry analysis versus specific microscopic models. |
| Friday, September 22, 2006 | Paul Fendley [Host: Genya Kolomeisky] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Topological Quantum Computation” |
| Friday, September 29, 2006 | Randy Ruchti [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Notre Dame University and NSF | |
| Physics Building | “The National Science Foundation, One Particle Physicist's Experience” |
| During a recent term of service on the High Energy Physics Advisory Panel (HEPAP), which jointly advises DOE and NSF on particle physics matters, the speaker was persuaded of the importance of direct participation by active research scientists in the process of federal funding for research and education programs. This view has motivated a temporary term of service by the speaker at the National Science Foundation. The presentation will provide a view of how the NSF conducts its business in Elementary Particle Physics, from the perspective of an university-based experimentalist and faculty member serving as a visiting program officer. |
| Friday, October 6, 2006 | Howard Carmichael [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | University of Auckland, New Zealand | |
| Physics Building | “Nonclassical Light and Glauber's Theory of Optical Coherence” |
| The year 2005 celebrated the seminal contributions of Albert Einstein to physics, including his treatment of the photoelectric effect and his introduction of the quantum of light. The same year saw Roy Glauber awarded the Nobel Prize in Physics -- ``for his contribution to the quantum theory of optical coherence''. My talk will explore the connections between Glauber's and Einstein's work, while at the same time posing the question...in what sense, exactly, does light act as a particle and not a wave? |
| Friday, October 13, 2006 | Bill Phillips [Host: Thomas Gallagher] | |
| 4:00 PM, Room 204 | NIST | |
| Physics Building | “"A Bose Condensate in an Optical Lattice: cold atoms meet solid state"” |
| An atomic-gas Bose-Einstein Condensate, placed in the periodic light-shift potential of an optical standing wave, exhibits many features that are similar to the familiar problem of electrons moving in the periodic potential of a solid-state crystal lattice. Among the differences are that the BEC represents a wavefunction whose coherence extends over the entire lattice, with what is essentially a single quasi momentum and that the lattice potential can be turned on and off or accelerated through space. Experiments that are not easily done with solids are often straightforward with optical lattices, sometimes with surprising results. |
|
Monday, October 16, 2006 Note Special Day |
Cass Sackett [Host: Dinko Pocanic] | |
|
3:30 PM, Room 204 Note Special Time |
University of Virginia | |
| Physics Building | “An Atom Interferometer Using Bose-Einstein” |
|
Tuesday, October 17, 2006 Note Special Day |
Nilanga Liyange [Host: Dinko Pocanic] | |
|
3:30 PM, Room 204 Note Special Time |
University of Virgina | |
| Physics Building | “Jefferson Lab Hall: A neutron spin structure program” |
| Friday, October 20, 2006 | Peter Arnold [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “The Plasma Physics of Quark-Gluon Plasma (a theorist's perspective)” |
|
Monday, October 23, 2006 Note Special Day |
Jongsoo Yoon [Host: Dinko Pocanic] | |
|
3:30 PM, Room 204 Note Special Time |
University of Virginia | |
| Physics Building | “Magnetically induced electronic states in two-dimensional superconductors” |
|
Tuesday, October 24, 2006 Note Special Day |
Seunghun Lee [Host: Dinko Pocanic] | |
|
3:30 PM, Room 204 Note Special Time |
University of Virginia | |
| Physics Building | “Almost everything that you'd like to know about frustrated magnets” |
| Friday, October 27, 2006 | Luis Orozco [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | University of Maryland | |
| Physics Building | “Conditional measurements in cavity QED” |
| One of the striking differences between the classical world and the quantum world is the measurement process. This opens interesting possibilities to study how a quantum system evolves after a measurement. We have implemented a cavity QED system, where an atom or a few atoms interact with a single mode of the electromagnetic field. This interaction is such that a quantum fluctuation, the emission of a single photon, is a large event. We are studying, by conditional measurements, the dynamics of the cavity QED system as it returns to steady state after a fluctuation and can now relate this to some of its intrinsic properties such as entanglement. |
| Friday, November 3, 2006 | Vladimir Kresin [Host: Stu Wolf] | |
| 4:00 PM, Room 204 | LBL | |
| Physics Building | “Potential Room Temperature Superconductivity in Metallic Nanoclusters” |
| Superconductivity is a peculiar state of matter which is manifested in such diverse fields as solid state physics, nuclear physics, astrophysics, biology, etc. In this talk we focus on small metallic nanoclusters (N 102-103 where N is the number of free carriers) which contain delocalized electrons. These electrons form shells similar to those in atoms or nuclei. It turns out that under special, but perfectly realistic conditions, superconducting pairing is very strong and can lead to high values of Tc. We have shown that for realistic sets of parameters one can observe very high values of Tc (Tc 102 K ) as well as a strong modification of the energy spectrum. Nanoclusters should form a new family of high temperature superconductors and in principle, it should be possible to raise Tc up to room temperature. We have proposed specific experiments aimed at detecting this phenomenon (e.g. spectroscopy and magnetic properties). This phenomenon is quite promising for the creation of high Tc superconducting tunneling networks. |
| Friday, November 17, 2006 | Csaba Csaki [Host: P.Q. Hung] | |
| 4:00 PM, Room 204 | Cornell University | |
| Physics Building | “Searching for the mechanism of electroweak symmetry breaking” |
| The standard model of particle physics has been very successful at explaining all collider experiments to date. However, it does not give a well-motivated explanation for why the electroweak symmetry should be spontaneously broken. Recently several new possible theories have been suggested to cure this shortcoming. I describe the motivations and the consequences of some of these new theories, including large and warped extra dimensions, higgsless and little higgs models. |
| Friday, November 24, 2006 | Thanksgiving Recess [Host: N/A] | |
| 4:00 PM, Room 204 | N/A | |
| Physics Building | “N/A” |
| Friday, January 19, 2007 | Dan Kaplan [Host: E. Craig Dukes] | |
| 4:00 PM, Room 204 | Illinois Institute of Technology | |
| Physics Building | “New Ideas in Neutrino Physics” |
| The existence of neutrinos -- neutral, massless, almost- noninteracting counterparts of the electron -- was first proposed in 1930, in response to apparently incomprehensible experimental results. Neutrinos have been a puzzle ever since! One indicator of their importance is the unusually large number of Nobel prizes awarded for neutrino work, the most recent in 2002. A brief account of the neutrino story will lead to a discussion of current issues in neutrino physics, including the intriguing possibility that neutrino interactions explain the existence of all matter in the universe. Techniques for the future study of neutrino physics will be described. |
| Friday, February 2, 2007 | Sang-Wook Cheong [Host: Seunghun Lee] | |
| 4:00 PM, Room 204 | Rutgers University | |
| Physics Building | “New magnetic twists for multiferroicity” |
| Friday, February 9, 2007 | Keith Williams [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Molecular Electronics- Past, Present and Future” |
| Friday, February 16, 2007 | Carlos Sa de Melo [Host: Joe Poon] | |
| 4:00 PM, Room 204 | Georgia Tech | |
| Physics Building | “The Evolution from BCS to Bose-Einstein Condensation: Superfluidity in Metals, Neutrons Stars, Nuclei, and Ultra-Cold Atoms” |
| > Superfluidity is a very interesting phenomenon that has been found in metals, > neutron stars, nuclei and more recently in ultra-cold atoms. For a given > metal, neutron star, or nuclei there is essentially "zero" tunability of the > particle density or interaction strength, and thus superfluid properties can > not be controlled at the turn of a knob. However, in ultra-cold Fermi atoms > the interaction strength and the particle density can be tuned to change > qualitatively and quantitatively superfluid properties. This tunability allows > for the study of the evolution from BCS (weak coupling) superfluidity of large > Cooper pairs to Bose-Einstein condensation (strong coupling) superfluidity of > tightly bound molecules. I will discuss the BCS to BEC evolution in s-wave > and p-wave angular momentum channels, and will conclude that this evolution is just a crossover phenomenon for s-wave, while a quantum phase transition takes place for the p-wave case. |
| Friday, March 2, 2007 | Avik Ghosh [Host: Keith Williams] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “The physics of nanoelectronic devices” |
| Nanoscale conductors, such as ultrasmall molecular wires, allow us to test our understanding of fundamental non-equilibrium transport physics, as well as explore new device possibilities. I will start with a generic treatment of current flow through a single energy level, and then generalize to include realistic bandstructure models and a full quantum kinetic theory of current flow. This allows us to interpolate between semi-empirical models that provide quick physical insights, and ‘first-principles’ models with no adjustable parameters. Using this formalism, we can quantitatively explain various experimental features and fundamental performance limits of molecular electronics. In the above treatments, we treat electrons as weakly interacting, operating in the ‘mean field limit’. However, ultra-short molecules are unique in that they often possess large electronic and vibronic correlation energies with prominent experimental signatures. Strong correlation requires a completely different transport approach in the molecular many-body Fock space that accounts for non-perturbative interactions. I will show that many features such as negative differential resistance, Coulomb Blockade, hysteretic switching and random-telegraph noise can be understood in terms of the dynamics of such many-body levels and their state filling under bias. A lot of the applications of nanoelectronics could involve bridging the mean-field and strongly correlated regimes, where the theory becomes particularly challenging. For instance, the tunable quantum coupling of current flow in present day silicon transistors with engineered molecular adsorbates could lead to devices operating on completely novel principles. |
| Friday, March 16, 2007 | David Weiss [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | Penn State University | |
| Physics Building | “Quantum simulations and quantum computation with atoms in optical lattices” |
| I will review the physics of 1D Bose gases, show how we experimentally implement them, and describe experiments that confirm the longstanding exact theory across all coupling regimes. I will also describe quantum Newton's cradles, which are out of equilibrium 1D gases that act unlike any other many-body system. Finally, I will show how we image 3D arrays of hundreds of single atoms, an important step on the way to making a neutral atom quantum computer. |
| Friday, March 23, 2007 | John Mather [Host: Brad Cox] | |
| 4:00 PM, Room 203 | Goddard Space Flight Center | |
| Physics Building | “From the Big Bang to the Nobel Prize and Beyond” |
| The Cosmic Background Explorer (COBE) satellite, proposed in 1974 and launched by NASA in 1989, measured the cosmic microwave and infrared background radiation from the Big Bang and everything that happened later. The COBE team made three key measurements: the spectrum of the cosmic microwave background radiation (CMBR) matches a blackbody within 50 ppm (rms), the CMBR is anisotropic, with 10 ppm variations on a 7o angular scale, and the cosmic infrared background from previously unknown objects is as bright as all the known classes of galaxies. The first measurement confirmed the Hot Big Bang theory with unprecedented accuracy, the second is interpreted as representing quantum mechanical fluctuations in the primordial soup and the seeds of cosmic structure and the basis for the existence of galaxies, and the third is still not fully understood. I will describe the project history, the team members, the hardware and data processing, the major results, and their implications for science, and end with the outlook for future progress with new background measurements and large telescopes such as the James Webb Space Telescope. I will show recent progress on building the JWST, with illustrations of the key technologies. |
| Friday, March 30, 2007 | Oleg Tchernyshyov [Host: Paul Fendley] | |
| 4:00 PM, Room 204 | Johns Hopkins | |
| Physics Building | “Topological defects in nanomagnets” |
| The interplay of local and long-range forces in ferromagnets leads to the formation of mesoscopic domains with sharp boundaries (domain walls). The physics changes drastically when the magnet size becomes smaller than the width of a domain wall. In submicron magnets the magnetization forms intricate smooth patterns that involve the more exotic topological defects: integer and fractional vortices, skyrmions, merons, and magnetic monopoles. I will describe recent experiments with these entities and our attempts to describe their static and dynamic properties. |
| Friday, April 6, 2007 | Haiyan Gao [Host: Simonetta Liuti] | |
| 4:00 PM, Room 204 | Duke University | |
| Physics Building | “A New Search on Neutron Electric Dipole Moment” |
| A new experiment is being planned to search for the neutron Electric Dipole Moment (EDM) with an unprecedented sensitivity. The proposed search aims at a two orders of magnitude improvement over the current experimental limit. A search for a non-zero value of the neutron EDM is a direct search of the time reversal symmetry (T) violation. It provides a unique insight into CP violation because of the CPT theorem. The Standard Model (SM) prediction for the neutron EDM is below the current experimental limit by six orders of magnitude. However, many proposed models of electroweak interaction which are extensions beyond the SM predict much larger values of neutron EDM. The new experiment has the potential to reduce the acceptable range of predictions by two orders of magnitude. Furthermore, if new sources of CP violation are present in nature beyond the Standard Model and are relevant to hadronic systems, this experiment offers a unique opportunity to measure a non-zero value of neutron EDM. The current understanding of the baryogenesis suggests that other sources of CP violation might exist in nature beyond the Standard Model and beyond what have been observed so far. To explain the baryon number asymmetry in the universe through the grand unified theory or electroweak baryogenesis, substantial New Physics in the CP violation sector is required. In this talk, I will discuss this new experiment following a brief review of previous neutron EDM experiments. |
| Friday, April 13, 2007 | Dr Daniel Green [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Fermi National Accelerator Lab | |
| Physics Building | “The CMS Experiment at the CERN Large Hadron Collider” |
| The US is heavily involved in the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Colllider (LHC). This new facility is explicitly designed to successfully search for the Higgs boson and generally to search for new symmetries of Nature such as Supersymmetry. The status of the LHC accelerator and the CMS experiment will be discussed as well as studies of the physics potential of CMS. |
| Friday, April 20, 2007 | Thomas Weinacht [Host: Bob Jones] | |
| 4:00 PM, Room 204 | SUNY Stony Brook | |
| Physics Building | “An Ultrafast Quantum Camera - Observing and Controlling Molecular Dynamics in Real Time” |
| Ultrafast laser pulses allow us to 'take pictures' of atoms and molecules on their natural timescales (~10 -14 s). They can also be used to exert very strong and controlled forces, allowing us to direct the dynamics of the system they interact with. I will describe a series of experiments which aim to control and measure the wave function for a molecule as it dissociates. The ultimate aims of our efforts are to use shaped laser pulses as 'photonic reagents' and to make 'molecular movies', which depict the evolution of the molecular wave function as a function of time. |
|
Wednesday, April 25, 2007 Note Special Day |
Larry Yaffe [Host: Peter Arnold] | |
|
3:30 PM, Room 204 Note Special Time |
University of Washington | |
| Physics Building | “Strongly-Coupled Plasmas and Gauge/String Duality” |
| The quark-gluon plasma produced in relativistic heavy ion collisions has been found to behave like a low viscosity fluid whose properties are very different from those of a weakly interacting gas of quarks and gluons. It is an example of a strongly coupled, strongly correlated system, for which perturbative approximation techniques are not adequate. However, it is now understood that certain 3+1 dimensional gauge theories, similar to QCD, may be exactly reformulated as string theories in higher dimensions --- and this "gauge/string duality" is easiest to use in the strongly coupled limit of the gauge theory. Under this duality, properties of a high temperature, strongly coupled plasma are directly related to gravitational dynamics around 4+1 dimensional black holes. Using this duality, it is possible to compute, reliably, dynamical properties such as viscosity, energy loss of heavy particles, and emission spectra in certain strongly coupled gauge theory plasmas. This talk will describe this progress and discuss its applicability to the quark-gluon plasma produced in current and upcoming experiments. |
| Friday, August 31, 2007 | Moses Chan [Host: Jongsoo Yoon] | |
| 4:00 PM, Room 204 | Penn State University | |
| Physics Building | “Can a solid be “superfluid” ?” |
| Abstract: At temperatures below 2.176K, liquid He-4 enters into a superfluid state and flows without any friction. The onset of superfluidity is associated with Bose-Einstein condensation where the He-4 atoms, which are bosons, condensed into a single momentum state and acquire quantum mechanical coherence over macroscopic distances. Recent torsional oscillator measurements of solid helium confined in porous media [1,2] and in bulk form [3,4] found evidence of non-classical rotational inertia indicating superfluid behavior below 0.2K. These measurements have been replicated in four other laboratories. Specific heat results will also be discussed. This work is done in collaboration with Eunseong Kim, Tony Clark, Xi Lin and Josh West and it is supported by the (U.S.) National Science Foundation. |
| Friday, September 7, 2007 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, September 14, 2007 | Keith Williams [Host: Genya Kolomeisky] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “A Century of Photo Physics: Mitchell Memorial Colloquium” |
| The fascinating history of photography actually extends back more than one millennium, with pre-modern chemical photography finally catching hold around the 1820s through the pioneering work of Niépce and his subsequent collaboration with Daguerre. Viable silver emulsions were developed shortly thereafter by Talbot and others, but it was not until the 1880's that Eastman introduced prototype, flexible films familiar to modern photographers. At the turn of the last century, Eastman's silver halide films had already revolutionized the art world, opened new doors in optical spectroscopy, and established an entirely new mode of journalism. However, the underlying physical process itself was not understood until the late 1930s, when Mott and Gurney published their theory of latent image formation. Until that point, photographic capabilities were still severely limited because latent images were not stable, and emulsions were still quite slow. J.W. Mitchell established a more comprehensive theory of latent image formation that laid the foundation for improvement. His important contributions defined a turning point in modern film photography, and helped to bring high-performance emulsions to the market, where they have dominated for a half century and are still preferred by many professional photographers today. This talk will provide a visual review of the past century of photography, providing examples of daguerreotypes, cyanotypes, kalotypes, and modern silver halide photographs in the context of their role in science, art, and journalism. I will also present a brief survey of recent developments in digital image capture and discuss my expectations for advances in the near future. This memorial colloquium is given in recognition of the contributions J.W. Mitchell, emeritus Professor of Physics at UVa. |
| Friday, September 21, 2007 | Ganapati Myneni [Host: Bellave Shivaram] | |
| 4:00 PM, Room 204 | JLab | |
| Physics Building | “JLab Scientific and Technological Advances with Commonwealth of Virginia Universities” |
| The Continuous Electron Bean Accelerator Facility (CEBAF) at Jefferson Lab in Newport News was established by the Department of Energy as a result of the initiatives from the faculty of Physics at the University of Virginia. Initially the design called for room temperature copper accelerator structures. However, the first director of CEBAF chose Superconducting Radio Frequency (SRF) Technology for the acceleration of the high quality electron beams. This led to many world class scientific and technological advances at JLab including the core SRF and 2 K refrigeration systems. In this presentation I would like to narrate the development of single crystal large grain niobium technology for the benefit of SRF accelerator cavities including the Ganni 2 K refrigeration cycle for the efficient cooling of these accelerator structures. Further recent innovations and evolution of 10 - 50 MeV beam test facility, efficient design of cryomodules and compact THz sources are also discussed. In addition the plans of bringing all these scientific and technological advances for the benefit of the commonwealth of Virginia Universities under the umbrella of UVa are also explained. |
| Friday, September 28, 2007 | Sergey Kravchenko [Host: Joe Poon] | |
| 4:00 PM, Room 204 | Northeastern University | |
| Physics Building | “Interplay of disorder and interactions in two dimensions” |
| The discovery of the metal-insulator transition (MIT) in two-dimensional electron systems challenged the veracity of one of the most influential conjectures in the physics of disordered electrons, which states that "in two dimensions, there are no true metals"; no matter how weak the disorder, electrons would be trapped and unable to conduct a current. However, that theory did not account for electron-electron interactions. Recently, we have investigated the interplay between interactions and disorder near the MIT using simultaneous measurements of electrical resistivity and magnetoconductance. It turns out that both the resistance and interaction amplitude exhibit a fan-like spread as the MIT is crossed. From these data we have constructed a resistance-interaction flow diagram of the MIT that clearly reveals a quantum critical point that separates the metallic state, stabilized by interactions, from the insulating state, where disorder prevails. The metallic side of this diagram is quantitatively described by the recent renormalization group theory (Punnoose and Finkelstein, Science 310, 289 (2005)) without any fitting parameters. |
| Friday, October 5, 2007 | Alex Meshik [Host: Keith Williams] | |
| 4:00 PM, Room 204 | Washington University, St. Louis | |
| Physics Building | “Natural Nuclear Reactor in Oklo” |
| Natural nuclear reactors were probably abundant on Earth about 2 billion years ago, but so far only 17 have been found in Equatorial Africa, just a few miles apart from each other. We will talk about how these natural reactors were predicted, searched for and discovered, and how the major characteristics of these reactors have been determined. Then we will show how isotope analyses of fission xenon led to realization of the operational mode of natural reactors and understanding of why the reactors did not explode just after they reached criticality.Finally, we will consider some physical, environmental and geochemical implications of this fascinating natural phenomenon. |
| Friday, October 12, 2007 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, October 19, 2007 | David Hofman [Host: Bob Hirosky ] | |
| 4:00 PM, Room 204 | University of Illinois Chicago | |
| Physics Building | “Creating a Quark Gluon Plasma with Heavy Ion Collisions” |
| It has now been seven years since a new era in relativistic heavy ion research began with the first beams at the Relativistic Heavy Ion Collider (RHIC). The primary goal of this effort was to heat a small volume of space so high that normal matter, comprised of protons and neutrons, dissolves into their constituent parts, the quarks and gluons, thus possibly creating a quark gluon plasma and perhaps even providing a window into how the universe may have looked in the first micro-seconds of its birth. In this talk, I will review the motivation and foundations for this endeavor, discuss several discoveries since RHIC began, explore a few of the more recent measurements, and look forward to what the very exciting and promising future will bring, especially in light of the startup of the new Large Hadron Collider in CERN. |
| Friday, October 26, 2007 | Aron Bernstein [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | Massachusetts Institute of Technology | |
| Physics Building | “Measurement of the π 0 Lifetime: Probing the QCD Axial Anomaly” |
| The π 0 lifetime has been measured with significantly improved accuracy at Jefferson Lab using the Primakoff effect. This was achieved by careful control of all of the experimental parameters and included auxiliary measurements of the Compton effect and pair production. This measurement is a test of a prediction based on the QCD axial anomaly plus few percent chiral corrections which are proportional to the mass difference of the up and down quarks. The basic physics, and a comparison of theory and experiment, will be presented in the context of spontaneous chiral symmetry breaking in QCD, some of its physical consequences, and other experimental tests. |
| Friday, November 2, 2007 | Reinhard Schwienhorst [Host: Bob Hirosky ] | |
| 4:00 PM, Room 204 | MSU | |
| Physics Building | “Physics with top quarks” |
| Experimental particle physics has reached a threshold that promises new and exciting insight into the fundamental structure of matter and the origin of particle masses in coming years. Due to its large mass, the top quark plays a key role in this quest for a deeper understanding of nature. We are currently learning a lot about the top quark through measurements at the Fermilab Tevatron. At the LHC at Cern, which starts in 2008, the top quark will become a probe for new physics and a tool for understanding mass generation. I will present our current understanding of the top quark and discuss its role in finding the new physics at the Tevatron and the LHC. |
| Friday, November 9, 2007 | Gabriel Aeppli [Host: Seung-Hun Lee] | |
| 4:00 PM, Room 204 | University College, London | |
| Physics Building | “Entanglement in real magnets” |
| Quantum entanglement is well-known to have consequences for optics and atomic physics, but is less recognized as impacting the properties of solids. Three examples - a dilute rare earth fluoride(Nature 425, 48), a transition metal oxide chain (Science 317, 1049), and a layered organometallic compound (PNAS 104, 15264), where entanglement matters for three real magnets are described. |
| Friday, November 16, 2007 | Barry Dunning [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | Rice University | |
| Physics Building | “Designer atoms: Engineering Rydberg atom wavepackets using pulsed electric fields ” |
| Advances in experimental technique now allow application of pulsed unidirectional electric fields, termed half-cycle pulses (HCPs), to Rydberg atoms whose characteristic times are much less than the classical electron orbital period. In this limit each HCP simply delivers an impulsive momentum transfer or "kick" to the excited electron. A number of protocols for controlling and manipulating Rydberg atom wavepackets using carefully tailored sequences of HCPs will be described with emphasis on the production of quasi one-dimensional and near circular Rydberg states, on navigating electron wavepackets in phase space, and on studying reversible and irreversible dephasing using electric dipole echoes. Insights provided by this work into classical-quantum correspondence, physics in the ultra-fast ultra-intense regime, and decoherence in mesoscopic quantum systems will be discussed. |
| Friday, November 30, 2007 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, December 7, 2007 | T. Egami [Host: Despina Louca] | |
| 4:00 PM, Room 204 | University of Tennessee | |
| Physics Building | “The Deep Puzzle of High-Temperature Superconductivity” |
| It is already 21 years since high-temperature superconductivity (HTSC) in the cuprate was discovered by Müller and Bednorz. At the beginning many theoreticians, including several Nobel Laureates, claimed they knew the answer. Even today, they keep claiming so, while they acknowledge that they actually do not know how to solve the problem theoretically. In the mean time experimentalists succeeded in making impressive improvements of their capabilities, and we now know the remarkable details of the cuprates physics and the HTSC phenomena. What emerged from the vast amounts of experimental results is the realization that while the existing theories can describe parts of the observed phenomena, something fundamental appears to be lacking from the theory. The puzzle may be deeper than people prefer to admit. In my view one of the most fundamental problems is that the transition from the Mott-Hubbard insulator due to strong electron-electron interaction to the Fermi-liquid state is an abrupt one, while any mean-field approximation makes it falsely continuous. In this talk I discuss evidences from neutron scattering experiments that this transition involves nano-scale phase separation, reflecting the discontinuity in transition, and how this conflict could contribute to the HTSC phenomena. |
| Friday, January 18, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, January 25, 2008 | Bernard Gerstman [Host: Art Brill] | |
| 4:00 PM, Room 204 | Florida International University | |
| Physics Building | “Protein Folding: Energy, Entropy, and Prion Diseases” |
| Living systems are the epitome of self-organized complexity. The self-organization occurs on all scales, from the molecular up to the organismal level. The machines responsible for maintaining organization are protein molecules that receive energy and convert it to work. However, protein molecules themselves must self-organize into highly specific shapes. The folding of proteins is a self-organizing process in which a long chain heteropolymer in a disorganized configuration spontaneously changes its shape to a highly organized structure in milliseconds. I explain how the energy and entropy landscape of protein chains is shaped to allow self-organization. I also show how these principles can be used in molecular level investigations of protein-protein interactions that lead to both beneficial dimerization or disastrous, disease producing and potentially fatal protein aggregation. |
| Friday, February 1, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, February 8, 2008 | Andrew Askew [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Florida State University | |
| Physics Building | “Life, the Universe, and Electroweak Symmetry Breaking” |
| One of the largest remaining questions in particle physics is the mechanism by which the W and Z bosons gain their mass. In the Standard Model of Particle Physics, this electroweak symmetry breaking occurs via the Higgs mechanism, though this remains experimentally unverified. I will overview this question and then concentrate on how diboson production and kinematics can give us information about this symmetry breaking. Experimental studies of boson pairs produced at the Tevatron and observed at the D0 experiment will be presented, ending with prospects for further study at the LHC. |
|
Wednesday, February 13, 2008 Note Special Day |
Zelimir Djurcic [Host: Brad Cox] | |
|
3:30 PM, Room 204 Note Special Time |
Columbia University | |
| Physics Building | “Searching for Physics Beyond the Standard Model with Neutrinos” |
| Although there has been tremendous progress over the past decade, many basic properties of neutrinos are still unknown and the possibility of future surprises remains strong. Recent neutrino experiments have conclusively observed that neutrinos have non-zero masses and that neutrinos change from one flavor to another. The MiniBooNE experiment at Fermilab recently presented its first neutrino oscillation results, where no significant excess of events was observed at higher energies, but a sizeable excess of events was observed at lower energies. The lack of a significant excess at higher energies allowed MiniBooNE to rule out simple 2-neutrino oscillations as an explanation of the LSND signal; however, the excess at lower energies is presently unexplained. Other data sets, including the NuMI, antineutrino, and SciBooNE data, should allow the collaboration to determine whether the lower-energy excess is due to background or to new physics. |
| Friday, February 15, 2008 | Marvin Blecher [Host: Blaine Norum] | |
| 4:00 PM, Room 204 | Virginia Tech | |
| Physics Building | “A More Accurate Measurement of Pion to Positron Decay” |
|
Tuesday, February 19, 2008 Note Special Day |
Sabine Lammers [Host: Brad Cox] | |
|
3:30 PM, Room 204 Note Special Time |
Columbia University | |
| Physics Building | “The Quest for the SM Higgs” |
| The Standard Model predicts the existence of one final particle, the Higgs Boson, which is the physical manifestation of spontaneous symmetry breaking as a mechanism for electroweak symmetry breaking, and is responsible for the masses of the known gauge bosons. Without the Higgs, the Standard Model is certainly incorrect or at least incomplete. We are at a precipice in the study of particle physics today because the answer to the question of the existence of the Higgs is about to be revealed. Constraints from precision LEP electroweak data indicate that the Higgs is light, making it within reach of observation by modern high energy particle colliders. I will discuss the state-of-the-art searches for the Standard Model Higgs Boson at the Tevatron and the plans for searches at the LHC. In particular, I will highlight the search techniques that are relevant at each collider and how Higgs searches at the LHC can benefit from knowledge gained at the Tevatron. |
|
Wednesday, February 20, 2008 Note Special Day |
Christopher Neu [Host: Brad Cox] | |
|
3:30 PM, Room 204 Note Special Time |
University of Pennsylvania | |
| Physics Building | “W Bosons and b Quarks at the Tevatron: Understanding the Haystack to Help Find the Needle” |
| Particle physics is at the threshold of an exciting new era. A crucial experimental pursuit is the search for and observation of the Higgs boson, a prominent missing piece in the widely successful standard model of the fundamental world. Searches at the Tevatron proton-antiproton collider in Illinois are closing in on the Higgs, while experiments at the new Large Hadron Collider in Switzerland are scheduled to begin operations later this year. One of the main signatures for the Higgs contains a W boson and one or more b quarks. However, this signature is shared by more common electroweak and strong processes that have not been determined precisely by experiment until now. Herein I will present a new measurement by CDF of W boson and b quark production. This measurement will contribute to improvements in the theoretical models, and I will discuss how this result can be used to sharpen searches for the Higgs and for physics beyond the standard model at both the Tevatron and the Large Hadron Collider. |
| Friday, February 22, 2008 | Benjamin Kilminster [Host: Brad Cox] | |
| 4:00 PM, Room 204 | Ohio State University | |
| Physics Building | “Fermilab's race for the Higgs boson” |
| One of the most important mysteries in our understanding of the universe is how elementary particles acquire mass. Our best explanation for this requires the existence of a particle called the Higgs boson, which has not yet been directly observed. Particle physicists at Fermilab, near Chicago, are currently capable of producing and detecting Higgs bosons from collisions of matter and antimatter at very high energies. I will explain what exactly these physicists are looking for, and present the experimental challenges involved in a few particular methods for differentiating Higgs bosons from other background processes. Finally, I will discuss future prospects for Higgs boson discovery at Fermilab, as well as the discovery potential of future experiments. |
| Friday, February 29, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, March 14, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, March 21, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, March 28, 2008 | Seonho Choi [Host: Nilanga Liyanage] | |
| 4:00 PM, Room 204 | Seoul National University | |
| Physics Building | “Probing Nucleons Inside Nucleus” |
| The interior world of the nucleus is still a mystery in nuclear physics. While it is well known that the nucleus is made of nucleons, their properties inside the nucleus are still a big puzzle. There has been a series of experiments to probe the nucleons inside the nucleus. However, the results are still controversial. One main remaining question is regarding the Coulomb Sum Rule (CSR). The colloquium will cover the basic concept of probing microscopic world with high energy electron beams, the key issues of the CSR problem and the recent, new experiment at Jefferson Lab to study the CSR problem. |
| Friday, April 4, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
|
Monday, April 7, 2008 Note Special Day |
Ned Seeman [Host: Keith Williams] | |
| 4:00 PM, Room Atrium | NYU | |
| Wilsdorf Hall | “Nanoscale Assembly with DNA” |
| Friday, April 11, 2008 | John Arrington [Host: Nilanga Liyanage] | |
| 4:00 PM, Room 204 | Argonne National Lab | |
| Physics Building | “Nucleon Form Factors...50 Years Later” |
| The structure of the proton and neutron can be expressed in terms of the electric and magnetic form factors which can be measured from elastic electron-proton scattering. Fifty years ago, the first electron scattering measurements of the proton form factors started the process of mapping out the distribution of charge and magnetization of the proton. Four decades of measurements gave us a simple picture of the nucleon, but our understanding was severely limited by the experimental techniques and theoretical understanding. The last ten years as provided several new experimental and theoretical techniques, giving us a much clearer picture of nucleon structure, and providing a few surprises along the way. |
|
Tuesday, April 15, 2008 Note Special Day |
Daniel Eisenstein [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Arizona | |
| Physics Building | “Dark Energy and Cosmic Sound” |
| I present galaxy clustering results from the Sloan Digital Sky Survey that reveal the signature of acoustic oscillations of the photon-baryon fluid in the first million years of the Universe. The scale of this feature can be computed and hence the detection in the galaxy clustering serves as a standard ruler, giving a geometric distance to a redshift of 0.35. I will discuss the implications of this measurement for the composition of the universe, including dark energy and spatial curvature. I will close with a more general discussion of SDSS-III, a new collaborative project that will feature a large redshift survey aimed at refining the acoustic oscillation distance scale to 1% as well as surveys for extrasolar planets and the structure of the Milky Way. |
|
Thursday, April 17, 2008 Note Special Day |
Alan Watson [Host: Physics Department] | |
|
7:30 PM, Room Chemistry Building, Room 402 Note Special Time |
University of Leeds, United Kingdom | |
| Physics Building | “The Birth of Cosmic Ray Astronomy on the Argentine Pampas” |
| Friday, April 18, 2008 | Alan Watson [Host: Brad Cox] | |
| 4:00 PM, Room 203 | Leeds University, England | |
| Physics Building | “Is the search for the origin of the highest energy cosmic rays over?” |
| This question can now be asked because of two results obtained using data recorded at the Pierre Auger Observatory. It has been established, at the 6-sigma level, that the flux of the highest energy cosmic rays is suppressed at energies beyond 5 x 10 19 eV and that above this energy an anisotropy in the arrival directions of the particles is apparent. The arrival directions appear to be associated with sources within the GZK horizon (z ~ 0.018 or 75 Mpc). From these observations it seems probable that we have observed the long-sought Greisen-Zatsepin-Kuzmin effect, demonstrating that ultra-high energy cosmic rays are of extragalactic origin. It is also probable that these particles are protons, thus offering the possibility of insights into features of particle physics at centre-of-mass energies 30 times greater than will be reached at the LHC. Preliminary conclusions from studies of detailed features of extensive air showers suggest that extrapolations from Tevatron energies may not be what have been anticipated hitherto. Much further work remains to be done. |
| Friday, April 25, 2008 | Kyungwha Park [Host: Keith Williams] | |
| 4:00 PM, Room 204 | Virginia Tech | |
| Physics Building | “Interaction between a molecular magnet monolayer and a metallic surface” |
| Over the past decade, molecular magnets or single-molecule magnets have drawn considerable attention due to observed magnetic quantum tunneling and interference and a possibility of using them for information storage or devices. There have been so far significant efforts to build and characterize thin films or monolayers of single-molecule magnets on surfaces or single-molecule magnets bridged between electrodes. However, there is need to understand changes of the properties of single-molecule magnets in those environments using atomic-scale simulations. In this regard, we simulate, within density-functional theory, a nanostructure in which prototype Mn12 molecules are adsorbed via a thiol group onto a gold surface. Based on a supercell calculation, we investigate how much charge and spin are transferred between a Mn12 molecule and the metal surface. In addition, we compare the electronic structure and magnetic properties of the nanostructure with those of an isolated Mn12 molecule in the absence and presence of spin-orbit interaction. |
| Friday, August 29, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, September 5, 2008 | Michael Raymer [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | University of Oregon | |
| Physics Building | “Photon Wave Mechanics and Spin-Orbit Interaction in Single Photons” |
| We often use the term “photon” in reference to individual quantum objects, or particles of light, rather than as excitations of the electromagnetic field. Yet, quantum mechanics textbooks contain no satisfactory wave equation for the photon wave function. I review the analog of the Dirac equation for a photon, which completely describes the evolution of the photon’s quantum wave function in coordinate space. Single photons carry orbital angular momentum as well as spin angular momentum. When a single photon travels in a multimode optical fiber, its spin and orbital angular momenta interact, modifying the shape of the photon wave function as it travels. Close analogy of this behavior can be found with that of an electron in a cylindrical potential, in spite of the fact that a photon has no magnetic moment. We are carrying out related experiments to illustrate the usefulness of the photon wave function concept. |
| Friday, September 12, 2008 | Alexander Kusenko [Host: PQ Hung] | |
| 4:00 PM, Room 204 | UCLA | |
| Physics Building | “Neutrinos, and the dark side of the light fermions” |
| The past decade has been marked by some remarkable discoveries in the neutrino physics: the particles once believed to be massless have turned out to be massive and have shown evidence of lepton family number violation, as well as other interesting phenomena. While this is exciting, the future may hold even more dramatic discoveries, the hints for which begin to appear in astrophysics and cosmology. The observed neutrino masses imply the existence of some yet undiscovered "right-handed" states, which can be very massive and unreachable, but which can also be light enough to constitute the cosmological dark matter and to account for a number of astrophysical phenomena, from supernova asymmetries and the pulsar kicks to the peculiarities in the reionization and formation of the first stars. I will review the recent progress in neutrino physics, as well as the clues that may lead to future discoveries. |
| Friday, September 19, 2008 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, September 26, 2008 | Oded Kishony [Host: Keith Williams] | |
| 4:00 PM, Room 204 | Charlottesville, Violinmaker | |
| Physics Building | “The Ancient Science of Violinmaking” |
| Friday, October 3, 2008 | Eun-Suk Seo [Host: Seunghun Lee] | |
| 4:00 PM, Room 204 | University of Maryland | |
| Physics Building | “Detecting Cosmic Messengers with Antarctic Balloon Flights ” |
| Cosmic rays bring us information about physical processes that accelerate particles to relativistic energies, the effects of those particles in driving dynamical processes in our Galaxy, and the distribution of matter and fields in interstellar space. These cosmic messengers can far exceed the energies produced by man-made particle accelerators on Earth. Balloon-borne instruments configured with particle detectors are flown in Antarctica to study cosmic-ray origin, acceleration and propagation. They are also used to explore a possible supernova acceleration limit and to search for exotic sources such as dark matter and antimatter. Our on-going efforts with balloon-borne experiments will be presented and challenges of extending precision measurements to highest energy practical will be discussed. |
| Friday, October 10, 2008 | Available [Host: ] | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, October 17, 2008 | Costas Soukoulis [Host: Michael Fowler] | |
| 4:00 PM, Room 204 | Ames Lab | |
| Physics Building | “Bending Back the Light: The science of negative refraction” |
| Friday, October 24, 2008 | Mark Adams [Host: Bascom Deaver] | |
| 4:00 PM, Room 204 | Vice President, ITT Corporation | |
| Physics Building | “Physics –Fundamentals for Business” |
| Mr. Adams discusses a number of poignant experiences as an undergraduate Physics major at UVA and traces how these lessons have been foundational in his approach to building businesses throughout his career. The technical and operational challenges of remaking a failed $7B company with annual losses exceeding $1B are described from the perspective of a closet physicist. Mr. Adams relates his physics inspired approaches – ranging from the futile to the fruitful – to creating an organization that supports over 300,000 subscribers in over 100 countries worldwide. He also discusses the physics behind his second business startup, which has grown to over a hundred professionals with locations in three states. |
|
Thursday, October 30, 2008 Note Special Day |
Seunghun Lee [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Magnetic field-induced phase transition in a quantum gapped system: is the Bose-Einstein condensation concept useful?” |
| Friday, October 31, 2008 | Bellave Shivaram [Host: Jongsoo Yoon] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “SCIENTIFIC CHALLENGES IN HYDROGEN STORAGE: BREAKTHROUGHS AT UVa” |
| I will describe results of recent experiments at UVa which have revealed that hydrogen storage upto 14 wt.% can be achieved. This is a world record for hydrogen uptake. I will also review the significant scientific challenges that remain and discuss possible solutions. Related work in other laboratories will be discussed as well. |
| Friday, November 7, 2008 | Carl Caves [Host: Olivier Pfister] | |
| 4:00 PM, Room 204 | University of New Mexico | |
| Physics Building | “Quantum-limited measurements: One physicist's crooked path from quantum optics to quantum information” |
| Quantum information science has changed our view of quantum mechanics. Originally viewed as a nag, whose uncertainty principles restrict what we can do, quantum mechanics mechanics is now seen as a liberator, allowing us to do things, such as secure key distribution and efficient computations, that could not be done in the realistic world of classical physics. Yet there is one area, that of quantum limits on high-precision measurements, where the two faces of quantum mechanics remain locked in battle. Using my own career as a convenient backdrop, I will trace the history of quantum-limited measurements, from the use of nonclassical light to improve the phase sensitivity of an interferometer, to the modern perspective on how quantum entanglement can be used to improve measurement precision, and finally to how to do quantum metrology without entanglement. |
| Friday, November 14, 2008 | Andy Sandorfi [Host: Blaine Norum] | |
| 4:00 PM, Room 204 | JLab | |
| Physics Building | “Novel Physics with Frozen-Spin Polarized Solid Hydrogen” |
| Friday, November 21, 2008 | Pierre Meystre [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | University of Arizona | |
| Physics Building | “Cavity optomechanics” |
| Recent experimental advances in laser cooling have brought macroscopic oscillators closer than ever before to operating in the quantum regime. Fundamental interest in this frontier lies in the fact that quantum mechanics has never been tested at such a macroscopic scale, particularly with respect to counter-intuitive effects such as superposition and entanglement. From a more practical point of view, mechanical oscillators operating in the quantum offer considerable promise as sensors whose precision is fundamentally restricted by quantum mechanics. The talk will present a broad review of the basic principles of the laser cooling of opto-mechanical cantilevers, and then turn to a discussion of some possible applications in the coherent control of atomic and molecular systems. |
| Friday, December 5, 2008 | Stefan Baessler [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “The study of neutron quantum states in the Earth's gravitational field” |
| I will discuss the discovery and characterization of gravitational bound neutron states. In the previous experiments, the lowest neutron quantum states in the gravitational potential were distinguished and characterized by a measurement of their spatial extent. The future detection of resonant transitions between these neutron quantum states with the help of the GRANIT spectrometer (under construction) promises to give further and more precise information. Here, transitions between different quantum states induced by RF pulses shall be observed. These measurements are not only demonstrations of standard quantum mechanics. I will discuss applications of these measurements in the search for spin-dependent short-range interactions. |
| Friday, January 16, 2009 | RESERVED | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, January 23, 2009 | Charlie Kane [Host: Israel Klich] | |
| 4:00 PM, Room 204 | U. Penn | |
| Physics Building | “The Quantum Spin Hall Effect and Topological Band Theory” |
| A topological insulator is a material with a bulk excitation gap generated by the spin orbit interaction, which is topologically distinct from an ordinary insulator. This distinction - characterized by a topological invariant - necessitates the existence of gapless metallic states on the sample boundary, which have important implications for electronic transport. In two dimensions, the topological insulator is a quantum spin Hall insulator, which is a close cousin of the integer quantum Hall state. In this talk we will outline our theoretical discovery of this phase and describe two recent experiments in which the signatures of this effect have been observed. (1) Transport experiments on HgTe/HgCdTe quantum wells have demonstrated the existence of the edge states predicted for the quantum spin Hall insulator. (2) Photoemission experiments on the semiconducting alloy Bi_{1-x} Sb_x have observed the signature of the gapless surface states predicted for a three dimensional topological insulator. We will close by arguing that the proximity effect between an ordinary superconductor and a 3D topological insulator leads to a novel two dimensional interface state which may provide a new venue for realizing proposals for topological quantum computation. |
| Friday, January 30, 2009 | Available [Host: Jongsoo Yoon] | |
| 4:00 PM, Room 204 | ||
| Physics Building |
| Friday, February 6, 2009 | Xiaochao Zheng [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Studying strong and electroweak interactions using electron scattering at Jefferson Lab” |
| I will present two research topics of Jefferson Lab: The first topic is focused on a planned precision measurement of the parity violating asymmetry in e-2H deep inelastic scattering (PVDIS). This asymmetry is sensitive to the electroweak neutral coupling $C_{2q}$ of the Standard Model. The experiment (E08-011) has been approved to run from November to December 2009. I will present the progress in the preparation of E08-011, in particular the development of a new fast-counting DAQ system. The second topic is on the extraction of double and single-target spin asymmetries of pion electro-production using JLab Hall B(CLAS)/EG4 data. We expect to extract these asymmetries in the very low $Q^2$ region Q^2<0.1 (GeV/c)^2. These data will provide important inputs to global analyses of the nucleon resonance structure. Preliminary results using a 3 GeV beam and a NH$_3$ target will be presented. |
| Friday, February 13, 2009 | Kent Paschke [Host: Dinko Pocanic] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Electrons and Mirror Symmetry” |
| Friday, February 20, 2009 | Richard York [Host: Blaine Norum] | |
| 4:00 PM, Room 204 | MSU | |
| Physics Building | “FRIB: A New Accelerator Facility for the Production of Radioactive Beams” |
| The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the “construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society.” A heavy-ion driver driver linear accelerator (linac) will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar to the linac beam, at near zero velocities after stopping in a gas cell, or at intermediate (0.3 to 10 MeV/u) velocities through reacceleration. An overview of the science and the design proposed for implementation on the campus of Michigan State University leveraging the existing infrastructure will be presented. |
| Friday, February 27, 2009 | Available | |
| 4:00 PM, Room 204 | ||
| Physics Building |
|
Thursday, March 12, 2009 Note Special Day |
Nathan Guisinger [Host: Keith Williams] | |
|
2:00 PM, Room 205 Note Special Time |
Argonne | |
| MEC | “Graphene-Based Electronics” |
| Friday, March 20, 2009 | Craig Dukes [Host: Jongsoo Yoon] | |
| 4:00 PM, Room 204 | University of Virginia | |
| Physics Building | “Beyond E=mc^2: Using Rare Particle Decays to Probe the Energy Frontier” |
| Although there is great excitement in particle physics these days, with the advent of the Large Hadron Collider upon us and the great discoveries we hope it will bring, for the first time in some seventy years there are no plans for any new accelerators to take us to the next energy regime. So we will need to look for tiny indirect signs such as rare particle decays in order to find out what may be lurking beyond what we can directly produce in collisions at particle accelerators. There is a long history of such searches for new physics, a history that predates particle physics itself. I will show how such searches will probe mass scales unobtainable by any conceivable particle accelerator and describe the types of accelerators and experiments that are being planned, in particular a very high-sensitivity search for lepton flavor violation in muon decays. |
| Friday, March 27, 2009 | Thad Walker [Host: Tom Gallagher] | |
| 4:00 PM, Room 204 | University of Wisconsin | |
| Physics Building | “Quantum Manipulation of Neutral Atoms Without Forces” |
| Interactions between pairs of Rydberg atoms can be so strong that the energy level structure of one atom is dramatically altered by the presence of a second atom 10 microns away. This "Rydberg blockade" is predicted to allow conditional quantum manipulation of individual atoms based on the quantum state of a distant neighboring atom. When successful, the resulting entanglement process occurs without the atoms experiencing any significant interatomic forces. I will describe experiments at the University of Wisconsin that demonstrate blockade-conditioned coherent evolution of a single Rb atom based on the quantum state of a second atom 11 microns away. Extensions of these ideas to deterministic single atom and single photon sources with atomic ensembles will be presented. |
| Friday, April 3, 2009 | Mike Norman [Host: Despina Louca] | |
| 4:00 PM, Room 204 | Argonne National Laboratory | |
| Physics Building | “High Temperature Superconductivity - After 23 years, where are we at? ” |
| The field of high temperature cuprate superconductivity remains as controversial as ever. Although certain matters have been settled, for instance the symmetry of the order parameter, there is no accepted microscopic framework for describing these materials. This might seem surprising given their relatively simple electronic structure, but the issues involved touch some of the most fundamental ones facing physics - in particular the problem of how to properly treat strong correlations between electrons. In this talk, I will discuss the progress that has been made, but also the many issues that will have to be resolved before we can say that we have "solved" the cuprate problem. |
| Friday, April 10, 2009 | Kirill Shtengel [Host: Israel Klich] | |
| 4:00 PM, Room 204 | UC Riverside | |
| Physics Building | “Non-Abelian anyons: New particles for less than a billion” |
| The notion of quantum topological order has been a subject of much interest recently, in part because it falls outside of the well-established Landau paradigm whereby states of matter are classified according to their broken symmetries. Topologically ordered phases cannot be described by any local order parameter, yet they have many peculiar properties clearly distinguishing them from the conventionally disordered phases. For example, in two dimensions, they may support anyonic excitations - the quasiparticles that are neither bosons nor fermions. Moreover, anyons with *non-Abelian* braiding statistics are expected to occur, particularly in the fractional quantum Hall regime. Interesting in their own right, such systems may also provide a platform for topological quantum computation. Interferometric experiments are likely to play a crucial role in both determining the non-Abelian nature of these states and in their potential applications for quantum computing. I will discuss solid state interferometers designed to detect such non-Abelian quasiparticle statistics. Should these experiments succeed, such interferometers could also become key elements in a topological quantum computer. |
| Friday, April 17, 2009 | Brad Marston [Host: Paul Fendley] | |
| 4:00 PM, Room 204 | Brown University | |
| Physics Building | “The Quantum Mechanics of Global Warming” |
| Quantum mechanics plays a crucial, albeit often overlooked, role in our understanding of the Earth's climate. In this talk three well known aspects of quantum mechanics are invoked to present a simple physical picture of what may happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase. Historical and paleoclimatic records are interpreted with some basic astronomy, fluid mechanics, and the use of fundamental laws of physics such as the conservation of angular momentum. I conclude by discussing some possible ways that theoretical physics might be able to contribute to a deeper understanding of climate change. |
| Friday, April 24, 2009 | George Gollin [Host: Craig Dukes ] | |
| 4:00 PM, Room 204 | University of Illinois | |
| Physics Building | “Academic Fraud and a Calculus of Death” |
| For a price, it is possible to acquire unearned academic degrees from non-existent universities that market diplomas over the internet. The most sophisticated of these diploma mill cartels, based in Spokane, Washington, used the turmoil in Western Africa to foster the illusion of recognition and accreditation by the Republic of Liberia. But these credentials were obtained through payments to government officials, and were no more legitimate than the supporting web of fake diplomatic missions, schools, accreditors, and credential evaluators created by the "Saint Regis University" group. Their operation spanned at least eighteen states and twenty-two countries, and their stable of degree mills included over seventy non-existent schools selling degrees in medicine, nursing, nuclear and aeronautical engineering, addiction counseling, and special education, among other fields. Falsely identifying herself as a Liberian official, the principal owner of St. Regis wrote to the University of Illinois in 2003 threatening legal action over information I had posted to a university web page. The resulting brawl led to a multi-agency federal criminal investigation: prosecutors indicted the owners and staff of St. Regis for mail fraud, wire fraud, money laundering, and bribery of foreign officials in late 2005. All eight defendants pled guilty; five began serving prison terms in late 2008. This is a serious issue. The investigation revealed an alarming mix of consumer protection, public safety, and national security issues raised by the activities of the Saint Regis group. In addition, the delay in Liberia's recovery from two decades of civil war, due to the corrupting influences of the St. Regis organization, convolves with Liberia's infant mortality rate in a ghastly calculus of death. And we now see a next-generation diploma mill, having learned from St. Regis' mistakes, attacking the higher education systems in the two African nations immediately to the west of Darfur. We are beginning to make progress. New federal legislation intended to begin the long process of obliterating the diploma mill industry is a direct result of the St. Regis case. Several states have also drafted new laws, or otherwise tightened their oversight of degree providers. But it is an international problem of great complexity, and we are slow to respond. I will tell you stories, all of which are true. |
| Friday, May 1, 2009 | Zlatko Tesanovic [Host: Seunghun Lee] | |
| 4:00 PM, Room 204 | Johns Hopkins University | |
| Physics Building | “Superconductivity at the Dawn of the Iron Age” |
| Recent discovery of iron-based high temperature superconductors hints at a new pathway to the room temperature superconductivity. The new materials feature FeAs layers instead of the signature CuO2 planes of much-studied cuprate superconductors. The antiferromagnetism also appears to be involved, although the d-electrons in FeAs seem considerably more mobile than their cuprate cousins. This high mobility, facilitated by a large overlap between atomic orbitals of Fe and As, plays a crucial role in warding off Hund's rule and the large local moment magnetism of Fe ions, the archrival of superconductivity. I will present a pedagogical review of the current status of the field, highlighting similarities and differences between iron pnictides and cuprates, and emphasizing the importance of the multiband nature of magnetism and superconductivity in these new materials. |
|
|
|
Maintained by the Webmaster This page was generated dynamically using content derived from our departmental database. |
Support UVa’s Physics Department |