| 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] |