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Spring 2006

Schedule Spring 2006

January 10, 2006
3:00 pm (Tuesday)

Dr. Wally Van Orden
Old Dominion University

A Brief Introduction to MathCad for Physicists

MathCad is a commercial computer program that provides a powerful and easy means of executing numerical and symbolic calculations. A brief introduction to the properties of MathCad will be presented including examples of solutions to selected Physics problems.

January 17, 2006
12:20 pm (Tuesday)

Note unusual time

Dr. Louis Bloomfield
University of Virginia

How Things Work: Physics in Everyday Life

In this talk, I will examine various objects of everyday experience and discover within them the physical concepts that make them work. In the process, we'll find that the world around us is rich with physics if only we take the time to look. On my agenda are roller coasters, bicycles, clocks, and microwave ovens and we'll address important questions such as: "why do you feel pressed into your seat as you go over the top of a loop-the-loop?" and "why shouldn't you put metal in a microwave oven?"


January 17, 2006
3:00 pm (Tuesday)

Dr. Louis Bloomfield
University of Virginia

Magnetism and Dynamics in Clusters of Atoms

Small aggregates of atoms often have properties that are intermediate between those of atoms and those of the bulk. But these clusters also have properties that are uniquely their own. Finite size and surface effects can lead to interesting behaviors in these small pieces of matter. This talk will discuss ongoing experimental work on the magnetism of transition metal clusters and on the picosecond dynamics of salt clusters near the finite-size equivalent of the melting transition.

January 24, 2006
3:00 pm (Tuesday)

Dr. Ian Balitsky
Old Dominion University

High-Energy Scattering in Quantum Chromodynamics

High-energy particle collisions probe the fundamental structure of matter at small distances. To search for a signal of new physics among hundreds of particles produced by the collision, one needs to understand the background coming from strong interactions described by Quantum Chromodynamics (QCD). After 30 years of study, considerable progress has been made in understanding the high-energy scattering in QCD, but we still do not have the complete theory. I will discuss the approach to high-energy QCD based on the effective degrees of freedom - Wilson lines or color dipoles.

February 7, 2006
3:00 pm (Tuesday)

Dr. Steve Manson
Georgia State University

Photoionization and Collisional Ionization of Atomic Systems

In recent years much has been learned both from theory and experiment concerning the ionization of atoms and atomic ions. Some examples of the new physics that has emerged will be presented including simultaneous collisional ionization of target and projectile, nondipole effects in low-energy photoionization, and multiple ionization at high energy. In addition examples of the synergy arising from the relationships between photoionization and collisional ionization, such as photodetachment studies, will be given.

February 16, 2006
12:30 pm (Thursday)

Note unusual date and time

Dr. Pieter Maris
University of Pittsburgh

From quarks to reality

A challenge in contemporary nuclear physics is to explain the confinement force that binds quarks and gluons within hadrons. The explanation must lie outside of perturbation theory. This is the subject of nonperturbative Quantum-Chromo-Dynamics (QCD). All nonperturbative physics is difficult but nonperturbative quantum field theory poses unique challenges. We suspect that QCD is the correct theory because on the energy domain appropriate to perturbation theory it agrees with experiments. This is due to ``asymptotic freedom'', whose discoverers were recently awarded the Nobel Prize in Physics. However, the real-world physics that QCD should describe includes properties of nucleons and other hadrons and their low-energy interactions. This involves energies far below that at which asymptotic freedom appears. In this nonperturbative domain, peculiar properties are evident. There is confinement. And there is dynamical chiral symmetry breaking: the nucleon's mass is 200-times that of a perturbative QCD quark -- the bulk of the nucleon's mass must come from somewhere else. I will explain tools and methods that can be used to connect QCD to experimental measurements, and to expose these peculiar properties as the natural consequence of QCD's interactions and symmetries.

February 21, 2006
3:00 pm (Tuesday)

Dr. Matthew Wingate
University of Washington, Seattle

Quarks, Neutrons, and Cold Atoms : A Lattice Window into Strongly Coupled Systems

Many of the questions we physicists try to answer can be split into parts: a leading part which is easily solved ("Consider a spherical cow"), plus corrections which can be made order-by-order in powers of a small parameter. There are a few interesting and important exceptions. For example, quarks do not naturally appear as isolated particles, but are confined to live in strongly bound states eluding such a perturbative description. These states, called hadrons, are the protons and neutrons, and their heavier cousins created for brief instants at particle colliders. There are many fundamental questions about quarks and their interactions which cannot be answered without a quantitative, nonperturbative approach. Another example is a dilute gas of strongly interacting fermions. At strong coupling we expect universal behavior: the physics is the same for dilute neutron matter as for cold atomic gases. Again this rich physics is inherently nonperturbative.

In this colloquium I will discuss lattice field theory, an approach to studying these nonperturbative systems quantitatively. Increased computational resources and recent innovations have overcome many of the hurdles impeding earlier progress. Now the field has begun a new era during which we can expect much better accuracy and many new applications. I will focus on the phenomenon of quark flavor mixing, where lattice QCD calculations are most advanced and results are contributing to the wider community. What mechanisms are responsible for a bottom quark changing to a down quark, for example, and how can lattice calculations help our investigations? I will also briefly describe my current effort to study dilute gases of fermionic atoms with lattice field theory.

February 23, 2006
12:30 pm (Thursday)

Note unusual date and time

Dr. Jozek Dudek
Jefferson Lab

The Physics of the GlueX Experiment - The Search for Hybrid Mesons

The GlueX experiment is a major feature of Jefferson Lab's 12 GeV upgrade program whose focus is the search for hypothetical 'hybrid' mesons in which the glue binding quarks becomes excited. I will discuss the basic physics behind hybrid mesons and the approach proposed by GlueX for their creation, photoproduction. Recent theoretical work within the conceptually simple flux-tube model and the more theoretically justified lattice QCD approach will be presented.

February 28, 2006
3:00 pm (Tuesday)

Dr. William Detmold
University of Washington, Seattle

Hadronic physics from lattice QCD

Understanding the physics of hadronic systems (protons, neutrons, pions, kaons, deuterons, etc) is an important task for two reasons. Firstly since hadrons account for 99.9% of the mass of our bodies and our bridges, being able to describe them accurately is obviously a major goal for physicists. Secondly, hadron physics provides the stage for many searches for new physics at the fundamental level (for example at the Large Hadron Collider soon to become operational at CERN in Geneva). The discovery potential of such experiments crucially depends on accurate descriptions of hadron structure and interactions.

March 2, 2006
12:30 pm (Thursday)

Note unusual date and time

Dr. Dieter Mueller
Arizona State University

A view inside the proton

With the Stanford Linear Accelerator a new era in particle physics started in 1966 yielding a new view of the world of elementary particles. It was realized that the proton with a radius of about 10^{-15} m is not elementary rather it is made of so-called partons. These particles were identified as quarks, hypothetically introduced by Gell-Mann and Zweig. The dynamics of quarks is described by Quantum Chromodynamics, which allows to analyze experimental measurements in terms of partonic degrees of freedom. In the last four decades both experimental and theoretical efforts lead to an impressive quantitative improvement of measurements, e.g., providing a precise knowledge of the longitudinal distribution of partons. More recently, the new concept of generalized parton distribution has been introduced and developed. In this framework the proton can be explored from a new perspective and the unsolved problem of the proton spin decomposition and the three dimensional distribution of partons in the proton can be addressed.

March 28, 2006
3:00 pm (Tuesday)

Dr. Thomas C. Killian
Department of Physics & Astronomy, Rice University; Houston, TX 77005

Pushing the Envelope of Plasma Physics: Ultracold Neutral Plasmas

Ultracold neutral plasmas, formed by photoionizing laser-cooled atoms near the ionization threshold, stretch the boundaries of traditional neutral plasma physics. The electron temperature in these plasmas is from 1-1000K and the ion temperature is around 1 K. The density can be as high as 1010 cm-3. Fundamental interest stems from the possibility of creating strongly-coupled plasmas, but recombination, collective modes, and thermalization in these systems have also been studied.

Using optical absorption imaging, we study expansion dynamics of the plasma during the first few tens of microseconds after photoionization. Images record the spatial extent of the system, while the Doppler broadened absorption spectrum measures the ion velocity spectrally. The expansion is driven by the pressure of the electron gas, so the ion acceleration depends on the electron temperature. Evidence for terminal ion velocity supports predictions of adiabatic cooling of electrons during expansion. Understanding expansion dynamics is important for plans to laser cool and trap the plasma.

This work is supported by the National Science Foundation and David and Lucille Packard Foundation.

*In collaboration with Priya Gupta, Sampad Laha, and Clayton. E. Simien.
[1] T. C. Killian, S. Kulin, S. D. Bergeson, L. A. Orozco, C. Orzel, and S. L. Rolston, Phys. Rev. Lett. 83, 4776 (1999).
[2] C. E. Simien, Y.C. Chen, P. Gupta, S. Laha, Y. N. Martinez, P. G. Mickelson, S. B. Nagel, T. C. Killian, Phys. Rev. Lett. 92, 143001 (2004).
[3] F. Robicheaux and J. D. Hanson, Phys. Plasmas 10, 2217 (2003), T. Pohl, T. Pattard, and J. M. Rost, Phys. Rev. A 70, 033416 (2004).

April 4, 2006
3:00 pm (Tuesday)

Dr. Cass Sackett
University of Virginia

Atom Interferometry using Bose-Einstein Condensates

Just as the laser revolutionized optical interferometry, it can be hoped that Bose-Einstein condensation will permit great advances in atom interferometry. Potential applications include inertial navigation, oil exploration, and measurements of chemical interactions. However, BEC interferometry also presents substantial challenges. Experiments to date have been limited to short interaction times, making precision measurements infeasible. It is thought that interatomic interactions are the main limiting factor. I will describe our recent implementation of a BEC atom interferometer that has been designed to minimize the effects of interactions and other noise sources, and I will discuss the prospects of implementing condensate interferometry on a truly macroscopic scale.

April 18, 2006
3:00 pm (Tuesday)

Dr. Xiao-Gang Wen

An artificial ether and origin of light

For a long time, we have been looking for ether -- a medium whose vibrations are waves that satisfy Maxwell equations. Here I will describe a way to make such a medium using a quantum spin system. We show that if spins form a string-net condensed states, then the vibrations of condensed string-nets are light waves (and the ends of strings are electrons). It is possible that our vacuum is a string-net condensed state and the elementary particles are merely collective excitations of a quantum spin system.

April 25, 2006
12:30 pm (Tuesday)

Note unusual time

Mr. Jack Mills and Mr. Jason Tracy
Old Dominion University

Senior Thesis Presentations

April 25, 2006
3:00 pm (Tuesday)

Dr. Julian Lower
The Australian National University

Investigating Atomic and Molecular Collisions Processes with Polarized Electrons

Studies of the ionization of atoms and molecules by electron impact are of interest both from fundamental and practical perspectives. In the former case, they enable us to investigate the complex behavior of systems of charged particles which underpins the electronic structure of matter. In the latter case they provide an enhanced understanding of the role played by ionization in a range of technological applications such as gas discharge, fusion physics and laser operation. I will describe how the application of sophisticated detector technologies and spin-polarized electron beams to collision experiments enables underlying mechanisms driving electron-atom/molecule collision processes to be highlighted. Recent experimental and theoretical results on the electron-xenon, electron-argon and electron-helium systems will be presented, illustrating how contributions from relativistic, exchange and many-body processes can be isolated and tested through judicious choices of targets and reaction kinematics.

May 2, 2006
4:00 pm (Tuesday)

Note unusual time

Dr. Boris Altshuler
Columbia University and NEC Laboratories America

Mesoscopic physics: from Brownian motion to quantum devices

One of the revolutionary papers that Einstein wrote in 1905 is devoted to the theory of the Brownian motion - motion of particles that are small enough to feel the molecular motion, and large enough to be observed individually. Einstein proposed statistical analysis of the motion of each Brownian particle and derived Diffusion equation to perform this analysis. This idea of statistical approach is so crucial for modern mesoscopic physics, that it would be fair to start the history of the field from the celebrated Einstein paper. Mesoscopic (sample-specific) effects are usually rather weak in classical systems. Quantum interference enhances them tremendously. Mesoscopic effects become increasingly important with miniaturization of the devices. As to the nanostructures, these effects simply dominate. We will briefly discuss the history and current status of the theory of quantum transport and its connection with the general description of complex quantum integrable and chaotic systems.