Faculty Research

Yakir Aharonov, a pioneer in the foundations of quantum theory, is well-known for his codiscovery of the Aharonov-Bohm Effect, which he made with the late physicist David Bohm. The Aharonov-Bohm Effect is one of a small number of cornerstones for optimizing quantum coherence in principle and in applications. Dr. Aharonov’s work has had a wide impact in many areas of modern physics, including optics, nuclear physics, chemistry, condensed matter physics, elementary particle physics, astrophysics, cosmology and laser and molecular physics. Some of the practical ramifications for the Aharonov-Bohm Effect include improving the technology in electron microscope holography (which is used in modern medical scanners) and quantum computing. Quantum computers store and process information with quantum states instead of with classical bits, then we can perform tasks that are not possible with digital computers, a possibility which could potentially transform much of science. Although Dr. Aharonov does not have any graduate students, his close collaborator, Jeffrey Tollaksen, Director of the Center of Quantum Studies does, and is interested in taking on additional highly qualified students.

Rob Cressman is an experimental biophysicist with a focus on neuronal dynamics and the physical mechanisms that underlie the activity supported by the brain. Dr. Cressman’s research borrows heavily from his training in non-equilibrium condensed matter physics, applying tools and theories from this field to these biological systems. In addition to being a member of the Department of Physics and Astronomy, Dr. Cressman is also a member of the Krasnow Institute for Advanced Study. His research is aimed at elucidating the fundamental dynamic modes that occur in normal as well as pathological brain function. Recent work has focused on the role of environmental variables, such as ion concentrations as a means to switch between different functional states of neuronal networks. Pathological behaviors like seizures and migraines are facilitated, if not generated, by the modulation of these parameters. Through mathematical modeling and experimentation we hope to understand the biological mechanism that normally maintain these variables in the hope of identifying targets and therapies that could control or even cure these afflictions. Dr. Cressman is currently supporting a single graduate student, but hopes to expand to several students in the near future.

Robert Ehrlich currently chairs the Department of Physics & Astronomy. His early research has been in experimental particle physics, with the most recent work in this area involving an analysis of data indicating that neutrinos might be tachyons, i.e., hypothetical partcles that travel faster than light. He recently did some unrelated work on an alternate mechanism for explaining ancient ice ages, based on solar diffusion waves. Most of his other publications in recent years have related to (a) physics education, (b) physics and society, e.g., women in science and global warming, and (c) communicating science to the broader public.

Robert Ellsworth does experiments to study cosmic rays and the properties of elementary particles. Both of these closely related lines of research involve large often international collaborations. The cosmic ray work is currently being done using the Milagro detector -- a water-Cerenkov experiment for the study of high-energy gamma rays produced in the galaxy. Milagro is a large, covered pool, located in the Jemez mountains near Los Alamos, New Mexico. It studies air showers produced by subatomic particles in the energy range 100 GeV to 100 TeV. Dr. Ellsworth’s elementary particle work, also done in a large international collaboration, is being done using “Ice Top,” which is part of a neutrino detector (“IceCube”) located at the south pole. Dr. Ellsworth has also been involved in work using the “Super-Kamiokande” neutrino detector, based in Japan, that reported the first evidence for neutrino oscillations, thus explaining he long-standing puzzle of the “missing” solar neutrinos. The existence of neutrino oscillations was important because it demonstrated that neutrinos cannot be massless objects, as had been previously believed. Currently, Dr. Ellsworth is not supervising student research projects on this work.

Harold Geller is currently involved with astronomy education research, in collaboration with the College of Education and Human Development's Center for Restructuring Education in Science and Technology, the MathScience Innovation Center, and the University of Virginia's Department of Astronomy. He taught and developed astronomy courses for teachers, and is currently working on a publication about best methodologies for teaching K-12 teachers astronomy. Dr. Geller is the Observatory Director, and is responsible for the implementation of the new 32-inch Richey-Chretien telescope to be delivered in 2008 to Mason's observatory at Research 1. He is working with Dr. Anthony Kaye on implementing a high resolution spectrograph to work with the new Mason telescope. Dr. Geller has a student assisting him in the use of the Department's small radio telescope, mapping the sky in the 21-centimeter wavelength, indicative of neutral hydrogen gas in interstellar space. Dr. Geller has a keen interest in astrobiology and developed the first course taught at Mason in astrobiology. He did graduate work with the Viking mission to Mars, the National Radio Astronomy Observatory using the 70-foot diameter dish for spectral analysis of unusual stars, and with the Solar Maximum Mission gamma ray spectroscope in a study of SS433.

B. Joseph Lieb is an experimental physicist who is also involved in computer simulations of planetary atmospheres. His research interests were originally in the field of experimental nuclear/particle physics including participating in experiments at several international particle accelerator facilities. Currently he is involved in an international collaboration using the COSY proton accelerator at the IKP laboratory in Germany. These experiments probe meson interactions with nuclei and the major focus is an attempt to detect the theoretically predicted existence of bound states of eta mesons in nuclei. Several years ago Dr. Lieb got involved in computer modeling of the Martian atmosphere based on the Caltech/JPL photochemical model. Included in the research that is currently in progress are detailed studies to predict the behavior of gases which might be indicative of subsurface life on Mars including CH4, HCN, H2S, NH3 and H2CO. These model studies include globally averaged-calculations, diurnal concentrations of these gases and their behavior at the surface-atmosphere boundary under various assumptions.

Yuri Mishin works in the areas of solid state physics and materials science, particularly on the theory and atomistic modeling of metallic materials. He is especially interested in physical properties of materials interfaces, atomic diffusion, thermodynamics and the mechanical behavior of crystals. His research is focused on metals, alloys and intermetallic compounds. Many them have important technological applications, such as high-temperature high-strength structural materials for aerospace technologies, electronic materials, and functional materials for nanotechnology. Such applications require a fundamental understanding of the physical mechanisms governing the structure-property relationships in the materials. The modeling and simulation method used by Dr. Mishin include molecular dynamics with classical potentials, various Monte Carlo schemes, phase-field modeling and other atomistic and continuum approaches. Currently Dr. Mishin has external funding to support a post-doctoral research associate and several graduate students, and he seeks to involve more students in this work. Specific areas of his research include:

Models of atomic interaction in materials.
Development of semi-empirical many-body interatomic potentials from experimental data and first-principles calculations.
Atomic structure and physical properties of interfaces in materials, including grain and inter-phase boundaries.
Interface motion, segregation, chemical reactions and cohesion.
Phase transformations at interfaces, faceting, melting and pre-melting.
Atomistic theory and modeling of interfacial kinetics in metallic materials.
Relationships between interfacial structure, chemistry, and diffusion.
Plastic deformation and fracture of metals, alloys and ordered intermetallic compounds. Role of grain boundary sliding and cleavage.

Robert Oerter has done research in supergravity theories, especially as applied to string theory, in quantum chaos, and in underwater acoustics. Currently, he is interested in nonlinear quantum mechanics and quantum computing. His book about the standard model of elementary particle physics, The Theory of Almost Everything: The Standard Model, the Unsung Triumph of Modern Physics, is a non-technical introduction to the most successful physical theory of all time, one that unites our understanding of the structure of matter and (almost) all of its interactions.

Brian O’Halloran’s research interests lies mostly in mid/far-infrared observations of starburst galaxies and active galactic nuclei, as part of studies concerned with galaxy evolution in the local universe, star formation in dwarf galaxies and the evolution of the interstellar medium in such systems. Starburst galaxies are currently undergoing a major epoch of star-formation that can dramatically alter the structure of the host galaxy and input large amounts of energy and mass into the interstellar medium. Understanding this feedback mechanism, particularly at high redshifts, is a key topic in understanding the structure and development of the earliest galaxies - studies of nearby targets allow us to probe galactic evolution at high spatial resolution and thus allow a baseline to be constructed for galaxy evolution at high redshift. In collaboration with others at GMU and the Spitzer Legacy SAGE program international collaboration of which he is a member (2007), we have studied a sample of nearby starburst galaxies at low and high metallicity in order to determine their star forming and ISM morphology, current state of star formation, the nature of their dust populations and the evolution of their local ISM as stellar population ages.

Merav Opher’s research has focused on the effects of magnetic fields in space physics and astrophysics. The objective of her research is to better understand crucial and fundamental magnetic field effects in space physics and astrophysics through theoretical and computational models in close correlation with existing data. Her approach is to use computer MHD simulations and the observational data as a guide to apply novel theoretical ideas. She uses computer simulations as a powerful tool to investigate novel magnetic field effects in astrophysical media closely tied to observations and investigated magneto-hydrodynamic instabilities in astrophysical media such as jets and stellar winds. Her group in involved in research in coronal mass ejections and their interaction with the solar wind, magnetic fields in disks around young starts, magnetic effects affecting the interaction of the solar system and the interstellar medium. Other subjects that we worked were: Interstellar Magnetic Field Direction, Radio emission in shocks, Magnetohydrodynamic instabilities in Jets of Solar like Stars, Magnetic Effects in Nuclear Reaction rates and Effect in Stellar Evolution, Magnetic effects in Shear Alfven waves, Primordial Nucleosynthesis affected by Magnetic Effects and Creation of Primordial Magnetic Field. External funding currently supports a graduate student and a post-doctoral research associate, and Dr. Opher seeks additional highly qualified students.

Jessica Rosenberg works on multiwavelength observational studies of galaxy populations in the local universe. A detailed understanding of local galaxy populations can provide constraints on how galaxies formed and how they evolve over time. In particular, she is involved with several large international radio astronomy collaborations using the Arecibo Telescope in Puerto Rico and the Nancay telescope in France to survey the gas in galaxies. These observations, in combination with optical data, will be used to examine the relationship between gas, stars, and dark matter in galaxies. They will provide tests of galaxy formation models and information on the processes that govern star formation and feedback in galaxies. Dr. Rosenberg is also leading a study of the dust and star formation in dwarf galaxies using the Spitzer Space telescope. The properties of these galaxies are interesting because they may resemble systems in the early universe. Dr. Rosenberg's research currently supports a graduate and an undergraduate student, and she seeks to find additional highly qualified students to work with her.

Phil Rubin is an experimental elementary particle physicist. As such, he is a participant in large-scale experiments designed to explore the fundamental components and interactions of nature. The experiments seek evidence for rare and forbidden sub-atomic processes which might be exceptions to accepted symmetries or conservation laws. He is currently involved in three experiments. In one of them being performed at the CERN lab in Geneva, the goal is to find possible evidence for “supersymmetry” in the decay of charged kaons. A second experiment, being undertaken using the Cornell linear accelerator is designed to study weak interactions of the charm quark.by looking for “forbidden” processes involving them. His most recent experiment is being conducted in China, and it is designed to study a particular property of neutrino oscillations, specifically one of the “mixing angles” of two types of neutrinos. This effort is an international collaboration comprised mainly of physicists from China and the U.S., but also including scientists and engineers from the Czech Republic, Hong Kong, Russia, and Taiwan, has been assembled. Dr. Rubin has involved students – both graduate and undergraduate – in this work, and would be interested in involving additional highly qualified students.

Indu Satija is a theoretical physicist working in the interdisplanry field of Condensed Matter and Nonlinear dynamics. Main focus of her research is the study of phase transitions in quantum systems. This includes Anderson transition induced by disorder, Mott transition driven by interactions between particles, magnetic phase transitions in quantum spin systems. Related topic is the localization transitions in quantum systems exhibiting chaotic behavior in the classical limit. Topics of immediate interest include phase transitions in the presence of non-Abelian fields, Berry phase, Bose Josephson Junctions and the study of higher order correlations to describe quantum phase transitions and quantum entanglement. Most of her research is strongly tied to experimental work in ultracold atoms in optical lattices at NIST and provides unique opportunities for both graduate and undergraduate research in exploring frontiers of quantum systems.

Karen Sauer directs The Magnetic Resonance Laboratory (MRL). The goal of the MRL is to understand and exploit spin-dynamics in such systems as nuclear quadrupole resonance and laser-polarized noble gas nuclei. In addition, we conduct experimental research to push the noise in such systems to their fundamental limit, to reveal the full capability of magnetic resonance at low-fields both as an analytic tool and for the detection of contraband substances. This research is currently supported by several external grants which supports two Ph. D. students. Funding exists to support additional well-qualified graduate students seeking to pursue research opportunities in experimental atomic physics.

Paul So is a theoretical physicist specialized in nonlinear dynamics. His previous work includes control theories for high dimensional chaotic systems, theories and experiments in quantum chaos, the characterization of synchrony in chaotic systems, and the dynamical reconstruction of nonlinear systems using both the observer technique and unstable periodic orbits. He is the co-director for the Center for Neural Dynamics within the University’s Krasnow Institute for Advanced Study. Dr. So’s recent research interests include network dynamics of neurons, the emergence of patterns in neuronal ensembles, the fundamental properties of nonlinear systems, and nonlinear techniques in analyzing neuronal data. Ultimately, this work promises to lead to a better understanding on the mechanisms for information processing in the brain and on dynamical causes related to neurological pathological problems such as epilepsy. For further details in the research being conduced at the Center for Neural Dynamics, please visit the website.

Michael E. Summers is a planetary scientist who specializes in the study of a variety of chemical and dynamical processes in planetary atmospheres. His work is primarily theoretical in nature, but he serves on several space mission science teams in the role of science planning and in the interpretation of spacecraft observations. Dr. Summers’ planetary research has dealt with the structure and evolution of the atmospheres of Earth, Venus, Mars, Jupiter, Io, Titan, Triton, Uranus, Pluto and its moon Charon. He is a member of the Science Team on the New Horizons mission to Pluto/Charon and the Kuiper Belt that was launched in January, 2006, and performed a flyby of Jupiter in February 2007. His research on the Pluto-Charon system focuses on understanding Pluto’s atmospheric structure and its rapid loss to space. His most recent work deals with the gravitational capture of Pluto’s expanding atmosphere by its moon Charon. His current research on the atmosphere of Mars is addressing some of the questions posed by the possible existence of subsurface life and the release of metabolic by-products that would serve as biomarkers. He is co-investigator on the NASA Langley Mars Airplane proposal that was a finalist for the first Mars Scout Mission. Dr. Summers’ work on Earth’s atmosphere has dealt with middle atmospheric ozone chemistry, the chemistry and dynamics of trace gases such as methane, water vapor, and carbon monoxide, heterogeneous chemistry on meteor dust, the influence of solar variability on the state of the stratosphere and mesosphere, and polar mesospheric clouds and their connection to climate. Dr. Summers’ current work on the terrestrial atmosphere deals with the sources and sinks of middle atmospheric water vapor and the role of water in the formation and evolution of Noctilucent Clouds. He is a member of the science team of the AIM (Aeronomy of Ice in the Mesosphere) Small Explorer mission that was launched in April, 2007 as the first dedicated mission to study the role of these high altitude clouds as indicators of global climate change.

Ming Tian’s research interests include laser atomic spectroscopy, nonlinear and quantum optics, and quantum information physics. The research activity is currently focused on rare-earth based solid state quantum memory and quantum computing, which are the important elements in developing quantum information science and technology. The research topics also include laser spectroscopic properties of rare-earth ions trapped in inorganic crystal lattice at cryogenic temperature, the coherent and incoherent processes under the excitation of composite laser pulses, and the influence of the static electric and magnetic fields. Study of these processes provides the information needed to set up the physical systems to demonstrate quantum memory and quantum computation and analyze and optimize the performance. Both experimental investigation and theoretical modeling are conducted in the research. Dr. Tian is currently supervising student research projects at both graduate and undergraduate levels, and she seeks to involve more students in this work.

Joseph Weingartner does theoretical astrophysics, with a focus on cosmic dust (i.e., sub-micron grains of solid material). Dust is nearly ubiquitous in the universe and plays critical roles in many astrophysical processes, including galaxy evolution and star and planet formation. Dr. Weingartner models the interactions between grains and their environment (including starlight, gas, and magnetic fields). Applications include the alignment of non-spherical grains with the interstellar magnetic field. Aligned grains polarize starlight and emit polarized thermal radiation; observations of this radiation can be used to learn about the geometry of the field. Dr. Weingartner supports undergraduate and graduate research students.