Physics

Faculty Research Summaries | Chairman's Introduction

Isaac D. Abella

In my research on Laser Coherent Transients, photon echo techniques are used to probe metastable excited states in rare gas mixtures such as helium, neon, and argon. The states are produced in a weakly ionized r.f. plasma discharge, and nitrogen-pumped dye lasers are used to generate the coherent super-position states.

I am also currently engaged with spectroscopy of rare-Earth laser material. Samples of YLF and YAG crystals doped with erbium, thulium, and holmium are being studied with selective laser excitation in the region of 780 nm, the erbium bands. These materials can be efficiently optically pumped by the AlGaAs-GaAs laser diode arrays, but we are using dye laser excitation. We are interested in the energy transfer process: Er to Tm, to Ho, which concentrates energy emission at 2.085 microns at room temperature and at liquid nitrogen. The process is a radiationless, almost resonant transfer of energy between sites and depends on the relative concentrations of the rare earth ions. In particular we are interested in measuring decay rates, excited state absorption, and branching ratios and detailed theories of such processes.

Edward C. Blucher

My current research involves studies of oscillations between different flavors of neutrinos. Recent observations of neutrino oscillations raise the exciting possibility of searching for violation of CP symmetry in the neutrino sector. The CP symmetry, which reverses left and right and changes particles into antiparticles, is thought to be necessary for understanding the striking asymmetry in the abundance of matter and antimatter in the Universe. The first step in this search is to detect the last unobserved type of neutrino flavor oscillation. Together with collaborators from France, Spain, Germany, U.K., Japan, Brazil, Russia, and the U.S., we are constructing an experiment to search for this last oscillation using neutrinos from a nuclear power station in northern France. The experiment, called Double Chooz, will begin taking data in 2009 and will run for a few years.

Our group is also completing several studies of CP violation in the neutral kaon system. Professors Wah, Winstein, and I, with a group of physicists from twelve universities, built an experiment called KTeV (Kaons at the TeVatron). The experiment collected data from 1996-2000, and established the existence of a new form of CP violation called direct CP violation. We are completing the analysis of this data sample to make the most precise measurement of direct CP violation along with many other parameters of the neutral kaon system. Our group also used the KTeV data sample to make a new measurement of the u-quark to s-quark coupling, resolving a more than 20 year old puzzle.

John E. Carlstrom

My research is focused on testing cosmological models of the universe. I pursue this research with new telescopes and instruments to image the intensity and polarization of the cosmic microwave background radiation, the fossil radiation from the early universe. Using our DASI telescope at the South Pole to make detailed measurements of the intensity variations and polarization of the background radiation, my research group has shown that the curvature of the universe is flat, supporting inflationary models and also providing a determination of the total density of the universe. We found that ordinary matter, the stuff of stars and us, accounts for only about 5% of the density. Another roughly 30% is composed of dark matter, presumably a yet-to -be-identified particle. Even less is known about the remaining, dominant component, the mysterious dark energy that apparently is causing the expansion of the universe to accelerate. We are building two new telescopes and detector systems to investigate the nature of dark energy by measuring its effect on the density evolution of the largest bound objects in the universe, clusters of galaxies. The Sunyaev-Zel'dovich Array (SZA) consists of eight 3.5 meter telescopes and is being deployed in California in Winter 2004. The South Pole Telescope is an 8-meter off-axis telescope to be deployed to the South Pole in November 2006.

Cheng Chin

I study the Bose-Einstein condensation of molecules and Fermionic superfluids. The formation and condensation of composite bosons by pairing fermionic atoms open the door to the exploration of superfluidity in different regimes. In the strong-coupling limit, atoms form short-ranged molecules, which undergo Bose-Einstein condensation (BEC) at low temperatures. In the weak-coupling regime, Cooper-pairing of atoms occurs in the Bardeen-Cooper-Schrieffer (BCS) state. In the crossover regime, the two types of superfluid smoothly connect to a new type of resonance superfluid, for which a universal behaviour is predicted.

I also study scalable quantum manipulation and quantum computation. Computation in the realm of quantum mechanics can be exponentially faster than its classical counterpart. In spite of the abundance of proposals to implement quantum computation, few systems have been experimentally demonstrated or can in principle be scalable to many quantum bits (qubits).

Ultracold atoms in an optical lattice formed by optical standing waves are a promising system to realize a scalable quantum computation system. By tuning the relative phase of the standing waves, arbitrary two atoms can be entangled by bringing them into close spatial vicinity. Repeating the above entanglement process on different atom pairs, we can establish quantum entanglement of many atoms. Since atoms can be individually trapped in the lattice with a typical periodicity of the optical wavelength, many qubits can be stored within a small volume of several cubic microns.

Philippe Cluzel

My research focuses on questions of noise and information in biological systems. Sudden changes of environment and life-cycle phases (growth, cell division, and death) characterize the conditions far from the equilibrium of chemical reactions occurring within individual cells. Yet cells, or more generally, biological systems, are able to process information accurately and to achieve precise tasks. How do biological systems use or circumvent these noisy conditions? Most of the experiments and mathematical models have assumed that the characteristics of the signaling and chemical reactions occurring within individual cells could be inferred from ensemble measurements. This approach, however, masks the temporal fluctuations and the dynamics of biological heterogeneous systems. A more promising alternative is to describe individually and in "real time" these strongly non-linear (living) systems. By developing novel single-molecule techniques, we can revisit canonical biological systems and question the advantage of "noise" for inter/intracellular signaling.

I also study noise in gene expression in bacteria. When few molecules are involved, chemical reactions are subject to stochastic fluctuations. Important steps of the gene expression in bacteria can be modeled by basic chemical reactions. A few molecules in the cell control these reactions. Consequently, the pattern of protein concentration growth is expected to be highly stochastic, exhibiting short bursts of variable numbers of proteins at varying time intervals. We are interested in characterizing experimentally the statistics of those simple chemical reactions that control the gene expression in individual living cells.

Finally, I study signaling in chemotaxis. The chemotactic system of E. coli (the network that governs the migration of bacteria towards chemical attractants) is used as a prototype for the study of intracellular signal transduction networks. Our approach is to consider the chemotactic network controlling cellular behavior as a biochemical circuit composed of independent modules. We identify the modules' contribution to the output within single living cells as well as the possible sources of their noise.

Juan I. Collar

My main interest is in the development of new methods for the detection for hypothetical astroparticles (WIMPs, axions, magnetic monopoles, any yet-to-be-discovered component of cosmic rays that might constitute a fraction of the 'dark matter'). Evidently, this is all risky business but I am interested in both journey and destination: the extreme levels of sensitivity sought in some of these experiments force us in the field to devise new detection approaches and to try to stay aware of the latest advances in particle detector technology. It is all a very enjoyable challenge. I am also attracted to other exotica such as double-beta decay (as part of the MAJORANA collaboration) and some 'hard' problems in neutrino detection (coherent neutrino scattering, detection of the relic neutrino sea). I enjoy the condensed-matter aspects of detector development, in particular the area of interactions between radiation and matter. I get easily excited about cross-disciplinary endeavors and real-life applications of detectors that may otherwise be chasing ghost particles.

Together with collaborators at the Groupe de Physique des Solides (Universite Paris VII), University of Lisbon, and Pacific Northwest National Laboratory, I developed large-mass, low-background superheated droplet detectors (SDDs) dedicated to WIMP (Weakly Interacting Massive Particle) searches (The SIMPLE dark matter search). In Chicago I was able to start investigating the possibility of making large bubble chambers stable enough for the same purpose. Much progress has been made (the Chicagoland Observatory for Underground Particle Physics, COUPP, using CF3I as an optimal WIMP target). At CERN I am involved in CAST, a search for solar axions using a decommissioned LHC test magnet, an interesting astroparticle spin-off from the Large Hadron Collider effort. More recently we started work on the application of new detector technologies to neutrino detection via coherent nuclear scattering.

Albert V. Crewe

I am involved in the development of high resolution electron microscopes, particularly scanning microscopes. I do work on theoretical and experimental electron optics, and the design of magnetic lenses and electron guns. My current emphasis is on the correction of spherical and chromatic aberrations which are the limiting factors in all present high performance instruments. A new type of corrector using magnetically focused electrostatic mirrors is now being tested, and the theory is being extended to full scale high performance systems. In addition we are exploring new concepts which will extend high resolution microscopy into the low energy arena (<1,000 volts).

James W. Cronin

James Cronin and University of Leeds professor Alan Watson lead an international project to study the nature and origin of rare but extremely powerful, high-energy (>1019 eV), cosmic rays that periodically bombard Earth. The project includes more than 250 scientists from nineteen nations.

The scientists will practice a new form of astronomy rooted in particle physics using the Pierre Auger Observatory, a giant detector array near the cities of Malargue and San Rafael in Argentina's Mendoza Province. The site contains 1600 particle detection stations 1.5 kilometers apart, arranged in a giant grid covering 3000 square kilometers, an area about the size of the state of Rhode Island. The Auger Project collaborators hope later to construct a complementary northern hemisphere observatory which, together with the southern observatory, would allow studies of cosmic rays from the entire sky.

Dean E. Eastman

My research interests include the development and application of leading edge synchrotron radiation techniques to interfaces, surfaces, thin films, and nanostructures relevant to future microelectronic devices and other novel material systems. Representative materials systems of interest include those relevant to (1) future Si CMOS-based technologies, (2) GaN and other III-V semiconductor films on Si and sapphire, and (3) multilayer magnetic thin film systems.

Synchrotron radiation techniques address physical structures; e.g., nanostructures, surface and interface structures, stress/strain distributions, dislocations, defects and doping distributions, as well as chemical and electronic properties. These techniques include various X-ray diffraction, microspectroscopy, microscopy, and other scattering techniques. Various types of photoelectron spectroscopy techniques (including band-mapping) using synchrotron radiation are used to study the electronic structure of surfaces, nanostructures, and solids. In addition to synchrotron radiation techniques, atomic scanning microscopy (STM, scanning tunneling microscope, and AFM, atomic force microscope) and STEM and SEM electron microscopy techniques offer powerful complemental capabilities to study physical and electronic structures.

This research utilizes leading edge synchroton radiation facilities (beamlines/end stations) at the Advanced Photon Source (APS), the Advanced Light Source (ALS) and others. It also involves collaborations with leading researchers in industry, at universities, and at government laboratories who provide samples, complementary characterization and processing capabilities as well as knowledge in addressing key questions and opportunities in advancing the state of the art. These advanced sample preparation and processing capabilities also facilitate studies of novel mesophysics phenomena involving nanostructures.

Peter G.O. Freund

From my work on the number-theoretic features of string theory connected with the algebraic geometry of the strings' world-sheets, I have been led to the study of certain two-dimensional integrable models which exhibit similar number-theoretic features. This has yielded new results on scattering processes in two-dimensional integrable quantum field theories. It has long been known that in such theories there is no particle production and the scattering of two particles determines the scattering of three or more particles. In a very large class of such theories, it turns out that even the input two-particle scattering is determined by simple considerations of quantum-geometry.

Geometries involving direct products of 4-dimensional anti-de Sitter (AdS) space with a 7-dimensional compact Einstein manifold, and of 7-dimensional AdS space with a 4-dimensional compact Einstein manifold which have appeared in the context of solutions of 11-dimensional supergravity found with M. Rubin, have recently been connected by Maldacena with conformal field theory in 3 and 6 dimensions. For certain cases this connection (and similar connections in other dimensions) have been studied in quite some detail by many authors. I am considering certain solutions of this type involving minimal supersymmetry or no supersymmetry at all.

We have constructed gravitational analogs of Born's nonlinear electrodynamics. In a very different vein we studied the implications of discrete scale invariance in certain rupture phenomena such as stock market crashes.

Henry J. Frisch

Our group is looking for Supersymmetry, Large Extra Dimensions, heavy right-handed quarks, new gauge bosons corresponding to new symmetries, and other new phenomena related to explaining electro-weak symmetry breaking, flavor, and the mass hierarchy. We have a wealth of new data from the CDF detector at the Tevatron, and are scheduled to continue running (taking data) through FY2009. The advantages of working at the Tevatron are that one can move fast into new and unique data, the groups one works with directly are small, and one should be able to make a topic ones own and finish a thesis quickly. In addition, the Tevatron can explore the lighter supersymmetric mass regions and make precision mass measurements of the W and top, a precision test of the Standard Model, which may prove very difficult at the LHC.

The analyses underway in our group at present with the new data from the ongoing run of CDF are: a search for Supersymmetry via the top quark decaying into a charged Higgs boson; for heavy right-handed quarks (postulated to explain the CKM matrix); searches for new heavy bosons and quarks such as would appear in large-extra-dimensions, and for anomalies in the photon+lepton+X sample, for which the light stop squark would be a good candidate (the stau slepton is another possibility).

In addition, our group is developing picosecond electronics and detectors for the identification of charged particles and the precise measurement of photon momenta. The electronics we are developing, with the Electronics Development Group of the Institute, is more than a factor of 100 faster than typical state-of-the art in HEP. We are also exploring the application of these techniques to medical radiolical applications (PET in particular).

This latter work is a wonderful way to learn cutting-edge instrumentation in a small group. I believe strongly that we train experimentalists and not `high-energy-physicists' or any other label; with a solid grounding in techniques one should be able to move among fields to go where the most interesting questions await.

More details on the beyond-the-Standard Model exploration and the instrumentation development are available on my home page at my home page.

Margaret Gardel

We are interested in the biological properties of the cytoskeleton of eukaryotic cells and how these regulate cell physiology. Cells generate protrusive and contractile forces in response to external chemical and mechanical stimuli and during cell migration. Improper regulation of the mechanical behavior of cells has been linked to a number of diseases, including asthma, cardiac arrhythmia and cancer metastasis.

The varied mechanical behavior of cells is determined by a dynamic and composite polymer network of > 100 proteins called the cytoskeleton. We develop tools to study the dynamic structure and biophysical behavior of macromolecular assemblies at sub-micron length scales to study how cells generate and transmit mechanical forces.

We use high resolution fluorescence microscopy to observe cytoskeletal protein dynamics in living cells and, simultaneously, measure their biophysical properties at micron length scales. By combining dynamic structure with biophysical measurements, we aim to elucidate the origins of the biophysical behavior of these assemblies. We are particularly interested in the biophysical behavior of contractile actomyosin networks and how these regulate how focal adhesion transmit force to the extracellular matrix.

Cytoskeletal material also provides quite a number of interesting problems in soft condensed matter physics. In contrast to traditional flexible polymers or rigid rods, cytoskeletal polymers are semi-flexible and the energy required to bend the filament on micron length scales is comparable to thermal energy. The competition between enthalpic and entropic effects in the dynamics and deformation of semi-flexible networks lead to extremely rich and varied mechanical response of both entangled solutions and chemically cross-linked networks. In the living cell, these networks are driven far from equilibrium by molecular motors and proteins that regulate filament cross-linking and assembly. We study the mechanical behavior of reconstituted networks of purified cytoskeletal proteins in vitro to better develop physical models of the elasticity of these dynamic semi-flexible polymer networks.

Robert P. Geroch

My research interests have been in three areas. The first is in the structure of the partial differential equations of physics. It turns out that there is a class of such equations (called first-order, quasilinear, hyperbolic systems) that, apparently, is sufficiently broad to encompass the descriptions of all (classical) physical systems. This class leads to a "universal" formulation of physical field theories. The second is the issue of describing quantum systems via Feynmann path integrals. There has been found a class of evolution operators for which such path integrals do exist, and this class of evolution operators, remarkably enough, includes candidates that are "close," in a suitable sense, to all bounded operators. Thus, this framework provides justification for the path-integral formulation of quantum mechanics. The third-an outgrowth of the second-involves the broad mathematical structure of measure and integration theory. It turns out that there is a framework for this subject-in which, for example, both the measures and the functions to be integrated are valued in abelian topological groups-sufficiently broad to encompass all physical applications of measure and integration, yet sufficiently narrow that the subject can be developed within this framework.

Ilya A. Gruzberg

I pursue research in two major directions. I briefly list relevant subjects, and then comment on them.

Mathematical physics: stochastic Loewner evolution, stochastic growth phenomena, conformal field theory, statistical mechanics, critical phenomena, random matrix theory, supersymmetry, algebraic and field-theoretical methods in condensed matter physics.

In the last few years, new insights have permitted unexpected progress in the study of fractal shapes in two dimensions. A new approach, called stochastic Loewner evolution (SLE), has arisen through analytic function theory and probability theory, and given a new way of calculating fractal shapes in critical phenomena, and in other problems like diffusion limited aggregation (DLA), the theory of random walks, and of percolation. This new method has close and beautiful connections to a number of older subjects: conformal field theory, random matrices and integrable systems. It has been already applied to such diverse problems as two-dimensional turbulence, spin glasses, and chaotic systems.

Condensed matter physics: disordered systems, mesoscopic physics, localization, quantum Hall effects, superconductivity, interplay of interactions and disorder, strongly correlated systems.

In this more traditional area I am mostly working on the theory of disordered systems, and in particular, on various aspects of localization phenomena: critical behavior at localization transitions, multifractiality of critical wave functions, and the like.

Philippe Guyot-Sionnest

My current researches focuses on two areas: quantum confined semiconductors and optical response of metallic nonostructures.

Quantum Confined Semiconductors. Delocalized electronic wavefunctions are readily achievable in semiconductor quantum dots, such as semiconductor nanocrystal colloids. This leads to extraordinary optical properties, which may lead to applications ranging from full-color displays, to photovoltaic cells. We synthesize semiconductor nanocrystals, and control their sizes and their surfaces. Microscopy and nonlinear spectroscopy are used to study the basic aspects of electron dynamics and interaction in strongly confined structures. We currently focus on the doping of nanocrystals and the very unusual infrared response, e.g. electrochromic, as well as the novel electrical transport properties in films made of these artificial atoms.

Optical Response of Metallic Nanostructures. Metallic structures much smaller than the wavelength of light allow to enhance locally the electromagnetic fields by several orders of magnitude. The enhancement is achieved by the plasmon resonance which is a collective excitation specific to the shape of the structure but involving all its free electrons. The enhancement is thus often limited by electron scattering process, in particular surface scattering which is increased in this small structures. Our research aims to synthesize metallic nanostructures, characterize their optical response, and optimize the materials combination to obtain much faster radiative emission of connected chromophores as well as giant optical nonlinearities.

Jeffrey A. Harvey

Much of the success of particle physics is based on situations where there is a small parameter (such as the fine structure constant in QED) and quantities of physical interest can be expanded in a perturbative series in terms of this small parameter. However there are many interesting problems for which this is not the case. These include confinement and chiral symmetry breaking in QCD and probably the questions of supersymmetry breaking and the choice of vacuum in string theory. There has been recent progress in these "non-perturbative" problems by using ideas based on supersymmetry and duality. Duality often allows one to reformulate non-perturbative questions in terms of a dual, weakly coupled description.

My current research focuses on using ideas of string duality to study the structure of QCD, the theory of the strong interactions. I am particularly interested in the structure of chiral symmetry breaking and the restoration of chiral symmetry at finite temperature and its possible experimental manifestations at the Relativistic Heavy Ion Collider.

I am also interested in many other topics in particle physics, cosmology and string theory. These include the structure of solitons such as magnetic monopoles, the development of techniques for better understanding M theory, the uses of anomalies in field theory and string theory, and the possibility of a non-commutative structure to spacetime at small distance scales.

Roger H. Hildebrand

Hildebrand and his students study interstellar magnetic fields by means of far-infrared polarimetry. Polarimetry at far-infrared and submillimeter wavelengths provides maps of magnetic fields in interstellar clouds as projected on the sky. The degree of polarization in molecular clouds depends strongly on wavelength. The polarization spectrum reflects emission from dust components that have different temperatures due to differences in exposure to heat sources, or, in diffuse regions, due to differences in emissivities of distinct grain species.

A polarimeter, SHARP, built in collaboration with Giles Novak - now at Northwestern University - and with other former Chicago students and colleagues,- makes it possible to pursue these topics with considerably improved resolution and sensitivity, and with passbands at both 350 and 450 microns. An archive of our previous results at 60 and 100 microns and results from other instruments at 850 and 1200 microns provide data for the first far-infrared/submillimeter spectra.

Among the topics under investigation are 1) turbulence in molecular clouds; 2) fields in external galaxies; 3) fields in Bok globules; 4) wavelength of minimum polarization in molecular clouds (< 350 microns?, > 350?, variable-cloud to cloud?); and, using polarization spectra from WMAP, 5) nature of anomalous microwave emission.

Heinrich M. Jaeger

My primary research interests are nanoscale physics and granular matter.
Nanoscale Physics. On size scales below typically one micrometer, metallic, superconducting, and semiconducting structures display properties which differ fundamentally from behavior on larger scales. In this so-called mesoscopic regime, the quantum nature of electrons leads to novel behavior not present in the macroscopic limit. We are investigating the electronic and magnetic properties of metallic and superconducting nanostructures. This research explores the roles of carrier confinement, quantum fluctuations, and disorder. We utilize experimental techniques such as cryogenic and high-magnetic field measurements, scanning probe and electron microscopy, and electron-beam lithography. Current research focuses on mechanisms for guided self-assembly of nanocrystal monolayers and metal-copolymer nanocomposites, and on the emerging novel electronic transport behavior. Another line of research probes the dynamical behavior of vortex matter (quantized magnetic flux bundles with nanometer-size diameters) inside type-II superconductors.

Granular Matter. Piles of dry grains of sand display a variety of behaviors that differ strikingly from those of ordinary gases, liquids, or solids. Macroscopic granular materials are typically found far from the most stable ("equilibrium") configurations. Ordinary temperature is irrelevant in driving granular systems; instead, they exhibit dynamic phase transitions in response to applied forces. An example is the transition from solid- to liquid-like behavior at the onset of particle flow and avalanching down the slope of a sandpile. In collaboration with Sidney Nagel, we have been investigating experimentally the complex, non-linear dynamics of granular flow and find that the behavior of granular materials has parallels in many other phenomena including magnetic flux creep in superconductors, charge density waves, and relaxation in spin glasses. Our current research investigates consequences of the inherently inhomogeneous force distributions inside granular matter, the glassy settling behavior as the system explores phase space, spontaneous structure formation and dynamic instabilities under applied stresses, and the propagation of energy and momentum through these highly dissipative materials. We use capacitive probes, high-speed video, magnetic resonance imaging (MRI), and x-ray tomography (at the Advanced Photon Source) to probe non-invasively the behavior of granular matter.

Leo P. Kadanoff

We work on non-linear systems using the techniques of statistical physics. More specifically, we are studying how turbulent, chaotic, and stochastic behavior arises in dynamical systems, particularly hydrodynamical and biological systems. For example, we have been extensively concerned with the development of simplified models for turbulence, with the nature of mathematical infinities in the flow of fluids and of bacteria, and with models of granular materials. We use both analytical and simulational methods and try to use experimental data whenever possible. Our basic goal is to understand the nature of the complex motion that can arise in even very simple systems. This work has applications to mathematics, astronomy, and chemical engineering.

I also do research and writing about the public presentation of science, particularly in the context of science museums. In the year 2007, I shall be President of the American Physical Society.

Woowon Kang

My research centers on the studies of novel, quantum mechanical effects in low-dimensional condensed matter systems. The collective response of a system consisting of many identical particles differs considerably from its single-particle behavior due to interaction between different particles. Unusual behaviors and phase transitions emerge as a classical system adiabatically enters the quantum regime. Model systems of interest include low-dimensional semiconductors and a class of charge-transfer molecular conductors. These systems serve as table-top testbed to study new types of ground states and excitations. Currently ongoing projects include:

Kwang-Je Kim

My general research interests are the Investigation of particle and photon beams and their mutual interactions with the goal of developing novel accelerators or radiation devices. Recent research topics include: the manipulation of particle beams in 6-D phase-space to reduce the size and cost of x-ray free electron lasers; the development of an electron gun with high brightness electron beams with flat transverse profile which can replace large and expensive damping rings in future linear colliders; and the development of an intense Terahertz radiator based on a Smith-Purcell backward wave oscillator using scanning electron microscope beams.

Young-Kee Kim

My main physics interests are to understand the origin of mass and the origin of the asymmetry between matter and anti-matter presently observed in our universe. Most of my current research is at the CDF (Collider Detector at Fermilab) experiment, a high energy physics experiment operating at the Tevatron, which brings together an international collaboration of over 800 physicists. Fermilab's Tevatron is currently the world's highest energy accelerator, colliding protons with antiprotons at a center-of-mass energy of 2 trillion volts. My group has played a major role in the detector construction and operation as well as in the data analysis from this experiment. In 1995, we, along with the sister experiment DZero, discovered the sixth and perhaps final quark, called the top quark.

Toward understanding the orgin of mass, the emphasis of my research has been the studies of the W boson (carrier of weak force, responsible for radioactive decays) and the top quark, nature's heaviest quark. Through quantum corrections, accurate measurements of the mass of the top quark and the mass of the W boson provide information about the mass of the Higg boson which is responsible for giving masses to elementary particles. My most recent work is in measuring the mass of the top quark. In addition, I am pursuing properties of the bottom quark, in particular its ability to mix into its antiparticle. This is an important measurement for understanding the phenomena of the asymmetry between matter and anti-matter.

David Kutasov

My main research focus in recent years was on a number of questions in field and string theory. One is the dynamics of strongly coupled field theories such as Quantum Chromodynamics, and in particular qualitative phenomena such as confinement and chiral symmetry breaking. String theory appears to be a very fruitful source of ideas for tackling these problems, and I have been involved in exploring their consequences.

Some other topics in string theory I have been studying are the evolution of black holes into highly excited strings as their mass decreases, the physics associated with cosmological singularities such as the big bang, the study of time dependent backgrounds that involve branes accelerating in an external gravitational field, holography in different types of backgrounds, infrared instabilities, and low dimensional toy models of string theory.

Generally speaking, I am interested in developing better tools for analyzing the consequences of string theory in various situations, which seems to be the main obstacle for making predictions about nature. I am also interested in using the dynamical mechanisms that were discovered in string and field theory in recent years to explain potential new results in particle physics experiments and cosmology.

Kathryn Levin

Our interest is primarily in theoretical studies of exotic superconducting and magnetic systems. We ask questions such as what makes different materials magnetic or superconducting? What is the nature of their superconductivity? The co-operative effects associated with magnetism and superconductivity lead to some of the most exciting and mysterious phenomena within the sub-field of condensed matter physics. Our experimental colleagues continue to discover and create new materials with fascinating properties, such as the heavy fermion and oxide superconductors. What distinguishes our sub-field of physics is the close and timely interaction between theory and experiment, as well as the long range possibility for making technological impact. This close theory/experiment interaction is at the heart of our research agenda.

While we have, over many years, been interested in the high temperature superconductors, we have now turned our attention to a new class of ultracold fermionic superfluids which are made by atomic physicists in atomic traps. We believe these "materials" may be prototypes of the cuprate superconductors and are particularly excited about the interesting problems which arise in these systems. How does one measure temperature? How does one prove superfluidity? The properties of this strange class of superfluids are intermediate between conventional (BCS) theory and Bose Einstein condensation. Most importantly, with the application of a magnetic field the system can be tuned from one behavior to another.

Riccardo Levi-Setti

A Scanning Ion Microprobe (UC-SIM) has been developed that performs Secondary Ion Mass Spectrometry (SIMS) imaging microanalysis of materials in the sub-100 nm range of lateral resolution. The mass analysis of the secondary ions is carried out with a high performance magnetic sector chemical mass spectrometer. This by now renowned instrument continues to find unique application in the study of advanced ceramics, in collaboration with DuPont scientists, and in a range of biological studies. The ability to detect isotopes is of extreme value in cytogenetics, allowing the distribution of labeled nucleosides to be mapped in human metaphase and Drosophila polytene chromosomes. In collaboration with scientists of the Department of Medicine of our University, investigations on the role of divalent cations in the scaffold structure of human metaphase chromosomes are in progress. Systematic studies of bone physiology continue also to be pursued in collaboration with researchers of the Department of Medicine of the University of Rochester, N.Y.

Zheng-Tian Lu

Testing time-reversal symmetry in atoms and nuclei.     We are searching for a permanent electric-dipole moment (EDM) of the 225Ra (t1/2 = 15 d) atom. A positive finding would signify the violation of time-reversal symmetry. This experiment provides an outstanding opportunity to search for new physics beyond the Standard Model. We have succeeded in realizing laser trapping and cooling of radium atoms (both 226Ra and 225Ra). At present, we are developing the techniques and apparatus needed for the EDM measurements with cold 225Ra atoms. See AIP News 812-3 (2007).

Radio-krypton dating.     The Atom Trap Trace Analysis (ATTA) method has revolutionized our ability to measure radiokrypton isotopes, 81Kr (t1/2 = 229,000 yr) and 85Kr (t1/2 = 10.8 yr), in samples of natural material. This in turn opens the door to a wide range of new applications in the Earth sciences. 81Kr measurements of groundwater samples from the Nubian Aquifer in the Western Desert of Egypt showed residence times approaching one million years. At present, we are developing the next generation instrument, ATTA-3, which is expected to further reduce sample sizes required for radiokrypton analyses of groundwater and glacial ice. See AIP News 679-3 (2004).

Studying exotic nuclear structure.     Helium-8 (8He) is the most neutron-rich matter that can be synthesized on earth: it consists of two protons and six neutrons, and remains stable for an average of 0.2 seconds. Because of its intriguing properties, 8He has the potential to reveal new aspects of the fundamental forces among the constituent nucleons. We have recently succeeded in laser trapping and cooling this exotic helium isotope and have performed precision laser spectroscopy on individual trapped atoms. Based on atomic frequency differences measured along the isotope chain 3He – 4He – 6He – 8He, the nuclear charge radius of 8He has been determined for the first time. The result can now be compared with the values predicted by a number of nuclear structure calculations and is testing their ability to characterize this loosely-bound halo nucleus. See AIP News 851-2 (2007).

Emil J. Martinec

My work aims at uncovering the structural foundation of string theory (now sometimes called M-theory), which attempts to unify the basic forces. The theoretical underpinnings of the subject are finally taking shape, due to the recent discovery of nonperturbative dualities between different descriptions of the theory. The spacetime manifold on which particles and waves propagate is being replaced by a more "stringy" notion of geometry at short distances and/or in strong fields. One issue of interest to me is how string theory incorporates black holes as quantum states. This problem has turned out to be a rather sensitive probe of the theory, and will likely lead us to new notions of space, time, and dynamics. Cosmology also requires an understanding of the resolution of gravitational singularities, and I am investigating whether techniques used in the resolution of black hole singularities can be applied there.

Gene F. Mazenko

Various materials, for example magnets, superconductors, liquid crystals, diblock copolymers and conventional solids, when temperature quenched from a high to a low temperature grow over time into ordered structures. In quenching a material from a temperature where it is a liquid down to a temperature corresponding to a solid we go from a material which is a uniform fluid to a final state where we have a crystalline solid. In the kinetic process taking us from the fluid to the crystal one finds intermediate states where the order is broken up by defects. Examples are dislocations in solids and vortices in magnets. We are interested in the appearance, motion and annihilation of these defects.

In the case of magnets and superfluids, where the final ordered state is uniform, the theory has been been developed to the state where we have been able to answer questions like: What is the velocity distribution for these evolving defects.

We are currently interested in the fundamental question of the nature of defect structures in pattern forming systems. Our interest is in those structures which form naturally under experimental circumstances. Our guide is to try and understand recent experiments on microphase separating diblock copolymer systems. Such systems grow a layered or striped phase. These systems are fundamentally important as prototypical two dimensional ordering systems but also as building blocks on the nano scale. Previously we have developed numerical techniques for looking at the nature of kinetic models proposed to describe systems of this type.

We are also working on the theoretical description of the kinetics of the liquid-glass transition. We have developed a new field theoretical model, called the hindered diffusion model, which leads naturally, to characteristic times which are activated, grow as eA/T as temperature T is lowered. Much remains to be worked out for this model.

Frank S. Merritt

I am working on the ATLAS experiment, which will begin taking data at CERN’s Large Hadron Collider (LHC) in 2007. The LHC will be by far the highest energy particle accelerator in the world, with beam energies 7 times greater than that of the Fermilab Tevatron and with a much higher luminosity as well. The LHC will explore the region of electroweak symmetry breaking, and will be able to cover virtually the entire domain of expected Higgs boson masses. It will be an almost perfect machine for searching for supersymmetry, which is the most likely extension of the current Standard Model of particle physics. There are certain to be surprises and a lot of interesting and fundamental physics (e.g., extra dimensions, new gauge bosons, surprises in the Higgs sector).

The Chicago group has been a key force in the development and construction of the hadron calorimeter (called the Tile calorimeter). We have developed much of the electronics, and are actively involved in the commissioning and installation of the experiment, which is beginning this year.

I have been working primarily in software development as the Tile reconstruction coordinator. I have recently become co-convener of the Jet-EtMiss Working Group, which is developing the software algorithms for jet reconstruction and jet calibration. This is central to almost all of ATLAS physics, and is especially critical to some of the most exciting physics discovery possibilities such as supersymmetry, since this will produce events with very significant amounts of “missing energy” carried away in supersymmetric particles.

There are a great many physics topics available and a great deal to do, both in preparation for data-taking in 3 years and in data analysis of the first events. The next 5 years will be a fantastically exciting time in ATLAS.

I am also a member of the OPAL experiment, which is finishing what has been an outstanding research program in physics at LEP. Before that I worked on the CCFR neutrino experiment at Fermilab.

Stephan Meyer

The TopHat experiment is a balloon-borne Cosmic Microwave Background (CMBR) anisotropy measurement designed to measure 5% of the sky in a region around the south celestial pole. The bolometric instrument has five channels sensitive to frequencies from 150 to 600 GHz. It is designed to have good rejection of galactic dust foreground emission and have sensitivity of about 25 muK RMS per 20 arcminute beam. To minimize systematic errors, the 1-M telescope is flown on top of a high altitude balloon in a circumpolar flight. This position permits observations at high elevation angle and with an extensive ground-screen with no strong sources high in the sky. The instrument is to fly in late December 1999 or January 2000 with a flight lasting about 10 days. With its sky coverage and sensitivity, the instrument will determine the shape of the CMBR anisotropy power spectrum in the region enveloping the predicted position of the first "Doppler Peak." The l-space resolution is high enough to easily resolve and measure the position and heights of the first two peaks in the power spectrum.

The Microwave Anisotropy Probe (MAP) satellite, scheduled to fly in December 2000, will measure the Cosmic Microwave Background Radiation (CMBR) aniostropy over the full sky in five frequency bands from 22 to 100 GHz. The angular resolution of the highest frequency is 12 arcminutes making the instrument sensitive to the CMBR angular power spectrum from l=2 to 500. Launched into an orbit that takes the satellite to the earth-sun L2 point, MAP will have extremely low systematic errors and with the complete sky coverage and sensitivity will answer many of the key cosmological questions of interest.

The Center for Astrophysical Research in Antarctica (CARA) is an NSF Science and Technology Center (STC) which began in February 1991. The center supports several astrophysical experiments, all based at the (South Pole Station, which have as a common thread the investigation of the evolution of astrophysical structure. The investigations range over scales from the measurement of the Cosmic Microwave Background Radiation (CMBR) anisotropy to measurements leading to a better understanding of star forming regions. The experiments are also related in that they all are made at centimeter to micron wavelengths which requires that they be carried out at a very cold dry site such as the South Pole. This is because the emission from water vapor in the atmosphere and the telescopes themselves limit the sensitivity for ground-based measurements in this spectral range. The experiments being carried out by CARA include: AST/RO, the Antarctic Submillimeter Telescope and Remote Observatory; Viper, a 2-M telescope optimized to observe the anisotropy of the CMBR and other low-surface brightness objects; Abu, a 1024 x 1024 element detector array; and the Degree Angular Scale Interferometer (DASI), an interferometric CMBR anisotropy experiment.

Dietrich Müller

Our research in high energy astrophysics includes the following topics:

Origin of high energy cosmic rays. Particle acceleration is an ubiquitous process in nature that occurs in all astronomical settings, from the surface of the sun to exotic, distant galaxies. In our galaxy, shock fronts from supernova explosions appear to be the sites where cosmic rays are accelerated over a large range of energies. However, the details of these processes are still poorly understood, and at the highest energies, above 1015 eV, other and as yet unknown sources of cosmic rays must exist. We aim to obtain observational constraints on the current models proposed for the origin of cosmic ray particles through precise measurements of the elemental composition and energy spectra of the individual cosmic ray components. Based on a series of investigations on high-altitude balloons and on the Space Shuttle, we have constructed a new and very large instrument, TRACER, that uses transition radiation detectors to permit measurements in the presently unexplored energy region between 1014 and 1015 eV. This detector exhibits a large sensitive area of nearly 5 m2, weighs about 3 tons, and is carried by stratospheric balloons above the earth's atmosphere, at a height of nearly 40 km above ground.

Search for anti-particles in the cosmic rays. Positrons and anti-protons are the only antiparticle species detected thus far in the cosmic radiation. They are generated subsequent to nuclear interactions in interstellar space and therefore provide an interesting probe on the structure of the interstellar medium and on the propagation of particles through the galaxy. However, there might also be more exotic contributions to the observed intensities of these particles, for instance, from the decay of hypothetical dark matter particles. These issues are studied with a balloon borne detector system, the High-Energy Antimatter Telescope (HEAT), which includes a superconducting magnet spectrometer. This instrument has been successfully flown in 1994 and 1995 to measure the flux of positrons and electrons over a wide energy range, and a modified detector system has been used for the observation of high-energy antiprotons in balloon flights in 2000 and 2001. This work is conducted jointly with Simon Swordy and collaborators at several other institutions.

Cosmic ray electrons at TeV energies. A new research project, CREST, has just been approved to search for cosmic ray electrons at energies above a few TeV. If they can be observed, such electrons must be generated rather close to the solar system, and their detection may lead to the discovery of specific nearby source regions. CREST is a balloon-borne instrument that will use a very unconventional technique: it will detect the electrons via their synchrotron photons emitted at x-ray and gamma-ray energies when the electrons traverse the earth's magnetic field. This work is conducted with Simon Swordy, and with collaborators at several other institutions.

Gamma-ray astronomy. A major frontier area in gamma ray astronomy is the region of high energies, from about 100 GeV to several thousand GeV. In this energy region, supernova remnants in our galaxy could be identified, demonstrating that these are indeed the sites where cosmic rays are generated, and exciting discoveries wait to be made with the observation of extragalactic objects. Detectors in space do not have sufficient sensitivity for these observations, but arrays of Cherenkov telescopes on the ground can observe the gamma-ray showers generated in the Earth's atmosphere. We participate in the construction of the VERITAS (Very Energetic Radiation Imaging Telescope Array System) installation in Arizona which has just begun and should lead to a 7-telescope array in 3-4 years. This work is conducted jointly with Simon Swordy, and in collaboration with a number of institutions in the US and in Europe .

Sidney R. Nagel

Many complex phenomena are so familiar that we forget to ask whether or not they are understood. Indeed, some effects are so ubiquitous that we hardly realize that they defy our normal intuition about why they occur. Examples of poorly understood classical physics include the anomalous flow of granular material, the long messy tendrils left by honey spooned from one dish to another, and the pesky rings deposited by spilled coffee on a table after the liquid evaporates. These are all non-linear hydrodynamic phenomena which not only are of technological importance but can also lead the inquisitive into new realms of physics. It is problems such as these which have fueled much of my research effort.

Another emphasis of my work can be classified as an attempt to understand the properties of disordered materials. I have worked on several different projects which involve a range of disciplines from conventional solid-state physics to non-linear dynamics with some applications to geophysics.

I list here a few of the topics on which my group is currently working:

Granular Materials. In collaboration with the group of Heinrich Jaeger, we have been studying the properties of granular media. Despite their ubiquity around us and the simplicity with which we can describe them, we understand very little about how these materials (e.g., sand) behave. In these studies we enter a new area of physics in which we are studying a statistical system of many particles but where the temperature is totally irrelevant. Thus, these systems are unavoidably always out of equilibrium, and we must come up with new concepts in order to understand and predict their properties.

Glass Transition. The glass transition has been called "the deepest and most interesting unsolved problem in solid state theory." We have been studying this transition using a variety of techniques including neutron diffraction, specific heat spectroscopy, computer simulation, dielectric susceptibility, shear modulus. We have managed to produce a master curve onto which all the dielectric data from all samples over 15 decades in frequency can be scaled. Such scaling has important implications for the nature of the glass transition.

Jamming. In an effort to deal with diverse phenomena where systems become stuck in a region far from equilibrium (e.g., at the glass transition and in clogged granular materials flowing-unsuccessfully-through a pipe), I have been investigating, along with Andrea Liu at UCLA, whether there can be a more general way of looking at these systems in terms of a "Jamming Phase Diagram." We proposed such a diagram and are currently investigating its utility in connecting a wide range of observed phenomena.

Singularities in Free-surface Flows. A drop falling from a faucet is a common example of a liquid fissioning into two or more pieces. The cascade of structure that is produced in this process is of uncommon beauty. As the drop falls, a long neck, connecting two masses of fluid, stretches out and then breaks. What is the shape of the drop at the instant of breaking apart? Something dire must happen to the mathematical description of the liquid at that point since the drop undergoes a topological transition where it starts out as a single, connected fluid and ends up in two or more separate pieces. This is an example of a finite-time singularity since the drop breakup occurs in a short time after the drop becomes unstable and starts to fall. At the transition, a singularity occurs since the radius of the neck holding the drop to the nozzle becomes vanishingly thin. As its radius goes to zero, the curvature diverges and the surface tension forces become infinite. How can such dramatic dynamics occur in something which had such smooth and innocuous initial conditions and forcing terms? Using photographic techniques, we have been studying transitions such as these to understand how the non-linearities in the governing equations (in this case the Navier-Stokes equations) can be tamed and understood. Singularities of this kind occur in many areas of physics from stellar structure to turbulence to bacterial colony growth. This drop breakup problem is one of the simplest places to start an experiment which directly probes the singularity itself.

Encapsulation of Biological Cells for Transplantation. Using the fluid experiments of the kind described above, in collaboration of Milan Mrksich in our Chemistry Department we have invented a new procedure for encapsulating small particles. This method may be particularly useful for coating biological cells for transplantation or for coating drugs for controlled time-release.

Crumpling. How does a sheet of paper crumple into a small ball? If you squeeze a sheet of paper very hard by hand, nearly 80% of the volume is still filled by air. What gives the crumpled ball its strength? We have been attacking this question experimentally in connection with the theoretical investigations of Tom Witten. We have found surprising time dependence and histeresis in the response.

Yoichiro Nambu

I have always been interested in the problem of mass hierarchy of particles. In this connection I have been exploring certain new aspects of spontaneous symmetry breaking. In 2002 I discovered a theorem on an anomaly in the number and the properties of Nambu-Goldstone bosons. This has led me to speculate on the possible violations of Lorentz invariance in free space. I also found that such “quasiparticles”, when regarded as classical particles, have peculiar non-Newtonian behavior that the effective mass can go negative (v and p in opposite directions) in a certain range of momentum, and the initial position and velocity of a particle do not uniquely determine its motion. In a more recent development, I have found a formulation of the so-called BEC-BCS crossover phenomenon, and I am looking into its general implications in physics.

Hagedorn-Rumer phenomena. It is well known in hadron multiple production (according to the so-called Hagedorn fireball model) as well as in string theory that the density of states increases exponentially with energy and competes with the Boltzmann factor so that thermodynamic equilibrium cannot be maintained above a certain limiting temperature. I have been interested in this as part of my search for phenomena that defy thermodynamics. The entropy of the black hole is of a similar but more drastic nature, and has been the subject of intense study in string theory lately. In classical physics I have found two simple examples of exponential density of states. One is a particle in a logarithmic potential, which had already been pointed out by Y. Rumer in 1960. The other is a particle under gravity and placed in a vessel whose horizontal cross section grows exponentially upwards. I suspect this is a rather general phenomenon which might eventually become relevant to biology as well as cosmological problems.

Reinhard Oehme

The confinement of gluons and quarks is a fundamental problem in non-perturbative quantum chromodynamics. Some time ago, we obtained results about the phase structure of ordinary and SUSY gauge field theories on the basis of superconvergence relations and the BRST cohomology. Now we find that, for SUSY theories, our conclusions agree with those obtained more recently on the basis of duality. In contrast to duality, our methods are applicable to non-SUSY theories.

As a general method of imposing restrictions on quantum field theories with several parameters, we have introduced a theory of reduction of couplings. This method is based upon the renormalization group, and is more general than the imposition of symmetries. There are solutions of the reduction equations which do not correspond to additional symmetries, but may be related to aspects of superstring theories. Our reduction theory is finding a wide range of applications. A comprehensive article for Physics Reports is in preparation.

Previously, in connection with the introduction and the proof of dispersion relations for hadron scattering, we have discussed effects of possible violations of locality and Lorentz invariance. With string theory, and in particular with field theories on non-commutative spaces, there are now more explicit models, and we are studying their implications. In addition to the absorptive thresholds and the composite structure cuts, there appear new singularities.

Mark J. Oreglia

I am a member of the ATLAS experiment at CERN, and this will be the main focus of my work for the foreseeable future.  My main interest is the search for new physics, particularly alternative models to the minimal Standard Model or minimal supersymmetric SM.  This continues my work on searches for SM and exotic Higgs bosons at LEP.

In addition to my ATLAS activities, I am involved in planning and detector R&D for the International Linear Collider (see the GDE site). I am co-spokesperson of the American Linear Collider Physics Group and a member of the CALICE R&D collaboration as well as the SiD detector concept.  To achieve the physics potential of ILC, there is must work to do in order to advance the state of the art for detector systems, particularly the concept of “particle energy flow”.

James E. Pilcher

My research involves studying nature at the shortest possible distances and highest energy densities. I have been engaged for several years in the preparation of the ATLAS experiment for the CERN Large Hadron Collider. This facility will enable the study of proton-proton collisions at a center of mass energy of 14 TeV or seven times that of earlier work. It will allow us to probe the source of electroweak symmetry breaking, and perhaps to understand why the Higgs boson is as light as the precision electroweak data predicts. The facility also has the potential to produce forms of matter never before observed. These include supersymmetric states, dark matter, heavy gauge bosons, and mini black holes. Some of these experimental signatures could also be associated with extra dimensions.

Our research group is closely involved in the preparation of the calorimeter of the ATLAS detector. This device measures the direction and energy of final state quarks and gluons and hence plays an essential role in the search for final states with apparent missing energy.

My earlier work involved high precision studies of the electroweak interaction using the OPAL experiment at the LEP e+e- collider. We measured the mass of the W boson to a precision of 0.06% to put new constraints on the electroweak theory and its prediction of the Higgs boson mass. We also made precise measurements of the Z boson total width and its decay rates to quarks and leptons. These results provided important additional tests of the theory.

Thomas F. Rosenbaum

At temperatures near absolute zero, new collective phenomena become possible. The quantum mechanical nature of materials is highlighted at the low temperatures, leading to a different class of phase transitions and to states with unusual excitation spectra. I use dilution refrigerator techniques to explore quantum magnets and glasses with connections both to quantum phase transitions and to the encoding of information, metal-insulator transitions with choreographed charge and spin degrees of freedom, new magnetoresistive compounds, vortex creep and tunneling, and exotic superconductivity. MilliKelvin temperatures often are combined with symmetry-breaking fields, such as uniaxial stress, to help constrain theory on fundamental grounds. These disparate topics are united by the theme of the interplay of correlation effects and disorder and by the issue of how macroscopic order can emerge from microscopic disorder.

Jonathan L. Rosner

Recent experiments at Fermilab and CERN and some non-accelerator experiments (including measurements of parity violation in atoms) have permitted tests of the theory of electroweak interactions with unprecedented accuracy. Studies are in progress to determine how these experiments shed light on new physics in the mass range of 100 GeV to several TeV.

A parallel line of investigation deals with the weak couplings of quarks to one another, as parametrized by the Cabibbo-Kobayashi-Maskawa (CKM) matrix. Various ways of learning these couplings more precisely are being studied. A key role is played by experiments on decays of mesons containing the "charm" and "bottom" (or "beauty") quarks. Present data on the violation of CP symmetry (the combination of charge and space inversion) in decays of these mesons are used to sharpen information on magnitudes and phases of CKM matrix elements and to search for new physics if and when inconsistencies are encountered.

Other topics being investigated include properties of systems involving one or more charm and bottom quarks, the nature of dark matter, the possibility that quarks and leptons have a composite structure, the role of neutrino masses in understanding fermion masses and couplings, the possibility of detecting new quarks and leptons with unusual quantum numbers as predicted in certain unified theories of the electroweak and strong interactions, and the experimental signatures of gauge theories beyond the standard SU(3) X SU(2) X U(1) electroweak-strong theory.

Robert Rosner

My research is mostly in the areas of plasma astrophysics and astrophysical fluid dynamics and magnetohydrodynamics (including especially solar and stellar magnetic fields); boundary mixing instabilities; combustion modeling; applications of stochastic differential equations and optimization problems; and inverse methods. I have continued research interest overlap with the DOE/ASCI Flash Center at Chicago (which I led for its first five years); this Center has been a pioneer in the development of computational astrophysics codes with broad applicability to other disciplines; and I have been closely involved in that Center's research activities in flame modeling and interfacial mixing. I have also been involved with a Wisconsin/Chicago/Princeton NSF-supported Physics Frontier Center focusing on problems lying at the boundary of astrophysics and laboratory plasma physics, mostly in areas related to magnetohydrodynamic instabilities in low Prandtl number fluids (such as liquid metals, or stellar interiors).

Guy Savard

My current research is centered around low-energy tests of the Standard Model of electroweak interaction. These studies are performed on samples of radioactive ions captured in ion traps where they are available for high-precision experiments. New techniques developed by our group to efficiently capture short-lived isotopes of essentially any species in ion trap allow us to select isotopes with decay properties which enhance and isolate specific effects and hence increase our sensitivity to the physics of interest. The present experimental program is looking at a more precise determination of the weak vector coupling constant and a more precise test of CVC and the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. A related experiment currently in preparation will search for scalar currents outside the standard V-A form for the charged electroweak interaction using samples of trapped superallowed emitters.

The type of experiment I am performing would greatly benefit from a more intense and versatile source of radioactive ions, and such a source has been assessed a high priority for new construction in nuclear physics in the US . I am therefore also heavily involved in the R&D for such a facility, which will use a novel technical approach for the fast extraction of the radioactive species based on some of the technologies we developed for ion trapping. (The leading contender for this facility is Argonne National Laboratory, located a short distance from Chicago .)

John P. Schiffer

Search for simple symmetries in nuclear structure using heavy-ion reactions; understanding dynamics of interactions between nuclear systems.

Study of crystalline order, phase transitions, and degrees of freedom in confined ionic systems in ion beams and ion traps.

Search for exotic objects in nature; e.g., particles of integral charge but anomalous mass such as strangelets, electron-positron peaks observed in conjunction with very high electromagnetic fields, "17-keV" neutrinos, etc.

Measurement of nuclear properties that are important in the processes of nucleosynthesis, with particular attention to the breakout point from the hot CNO cycle that is crucial in producing elements heavier than oxygen, and to the properties of some of the nuclei that are the principal visible remnants of supernova explosions.

Savdeep S. Sethi

To answer basic questions about the nature of space and time and the origin of the universe, we require a quantum theory of gravity. The most promising candidate for such a theory is string theory which attempts to unify all the forces of nature in a single consistent framework. String has grown much richer over the past few years, and is no longer simply a theory of weakly interacting strings. Rather it contains membranes and other higher-dimensional objects which all appear to originate from a unique eleven-dimensional theory known as M-theory. Uncovering the structure of M-theory is very likely to radically change our understanding of space, time and gravity.

My research centers on understanding various aspects of M-theory, string theory and field theory. Specifically, my recent work has focused on constructing models of the Big Bang where the physics near the Big Bang is actually under control via the use of holography. In such models, gravity and space-time are emergent phenomena. In addition to this area, I have long standing interests in string compactifications like those that involve fluxes or novel vacua that involve triples of commuting connections, and in supersymmetric field theory.

Melvyn J. Shochet

My research involves interactions between elementary particles at the highest manmade energies. For many years, this has been carried out with the Collider Detector at Fermilab (CDF), a massive detector that we built to study collisions between 1000 GeV protons and 1000 GeV antiprotons. With the large accumulated data sample, we have studied the strong and electroweak interactions and searched for new phenomena. Our most important result is the discovery of the top quark and the determination of its mass. Our latest top-quark mass measurement, which employs a new technique for significantly reducing the major systematic uncertainty, is (173.4 +/- 2.8) GeV, by far the most precise measurement of the mass of any quark. From this value, one can calculate the top quark's Yukawa coupling constant, the strength of its interaction with the Higgs Boson, the source of an elementary particle's mass. The Yukawa coupling constant for the top quark is 0.996 +/- 0.016, consistent with 1. This coupling to the source of mass is strong, unlike that of any other elementary particle, making it plausible that the top quark plays a special role in physics.

My group is now working on the ATLAS experiment at the CERN Large Hadron Collider (LHC), which will produce collisions 7 times more energetic than those at Fermilab. Our focus is an upgrade to the trigger, which selects interesting collisions in real time for later study. Hadron collider experiments can efficiently and quickly select events that contain electrons, muons, or generic hadron jets. However it is much more difficult to identify heavy elementary particles, the bottom quark and tau lepton, because of very large backgrounds. The new phenomena that should appear at the LHC will likely be characterized by the creation of heavy particles. This makes triggering on bottom quarks and tau leptons a priority. We are designing a set of trigger electronics boards that can identify these objects more than an order of magnitude faster than can otherwise be done. This device is based on the very successful Silicon Vertex Trigger (SVT) that we and our Italian colleagues built for CDF.

Simon P. Swordy

My research is directed to observations and analysis of high-energy radiation from space mainly through the following experimental efforts. I am involved with several projects to make measurements of high energy gamma rays and cosmic ray particles:

The VERITAS experiment (Very Energetic Radiation Imaging Telescope Array System) is a collaboration formed to build the next generation of atmospheric Cherenkov telescopes for gamma ray measurements in the TeV energy region. This is an an array of four 12m telescopes located near Tucson, Arizona. This new generation of gamma-ray detectors provides an increase in sensitivity of more than an order of magnitude compared to previous instruments. This instrument provides a unique view into the most energetic environments of our Universe while providing a host of new scientific opportunities. VERITAS can be used to directly search for direct evidence connecting supernova remnant sources to the origin of cosmic rays. VERITAS can also discover extra-galactic AGN Blazar objects out to redshifts of z~0.2. The interaction of TeV photons with intervening radiation fields in our universe can be used to investigate properties of early star and galaxy formation.

The CREAM experiment (Cosmic Ray Energetics And Mass) is a high altitude balloon experiment to directly measure cosmic ray composition using transition radiation and thin calorimetry. This experiment performed a record-breaking flight of over 40 days around the Antarctic continent in 2004-2005. The data from this experiment is at present under analysis, it is designed to measure the history of cosmic rays in the galaxy in the 100 GeV energy region for the first time.

Michael S. Turner

My research focuses on the application of modern ideas in elementary-particle theory to cosmology and astrophysics. I believe that this approach holds the key to answering the most pressing questions in cosmology. For example, there is reason to believe that the ubiquitous dark matter that holds the Universe together is elementary particles left over from the earliest moments, that the primeval inhomogeneity in the distribution of matter, which was revealed by COBE and which seeded all the structure in the Universe seen today, arose from quantum-mechanical fluctuations occurring during a very early burst of expansion called inflation, and that the existence of ordinary matter resulted from particle interactions in the early Universe that make the proton unstable and do not respect the symmetry between matter and antimatter. By testing these ideas with cosmological data, outer space becomes a window to the earliest moments of creation and to the unification of the forces and particles of Nature.

Over the next decade the search for particle dark matter, the mapping of the distribution of matter in the Universe a few hundred thousand years after the beginning through precision measurements of the cosmic microwave background radiation, and the mapping of structure in the present Universe by determining the positions of millions of galaxies should definitively test these bold ideas. Much of the crucial experimental work is being done by colleagues at Chicago; for example, the Sloan Digital Sky Survey will map the positions of a million galaxies and the DASI, TopHat, MAP, and Python experiments will measure the fine-scale anisotropy of the cosmic microwave background radiation.

Current specific areas of research include: big-bang nucleosynthesis in era of precision cosmology; theoretical aspects of inflationary cosmology; testing the inflationary paradigm; determining the nature of the dark energy that is causing the Universe to accelerate; dark matter and dark-matter detection; dark matter and the formation of structure in the Universe; the origin of the cosmic asymmetry between matter and antimatter; understanding how to use precision measurements of the fine-scale anisotropy of the cosmic microwave background and large-scale structure to probe inflation and fundamental physics; and aspects of axion, neutrino and string cosmology.

Carlos E.M. Wagner

Among the most relevant open questions in particle physics are the ones related to the origin of mass and to the existence of matter in the Universe. The answer to the first question relies on the mechanism of electroweak symmetry breaking, which can be tested through the corresponding Higgs physics at high energy collider facilities. The answer to the second question is more difficult, since the understanding of the origin of ordinary matter, the building blocks of atoms, and of dark matter, visible only via its gravitational interactions, demands new physics, beyond the current Standard Model description. One ambitious goal would be to find a scenario that led to an answer to all these questions in a natural way. Supersymmetric extensions of the standard model seem to provide the best framework to achieve such a goal, while allowing the possibility of a unified description of all particle interactions. For these reasons, my research activities focus on such supersymmetric extensions, putting emphasis on Higgs physics and on the possible experimental tests of these theories. Moreover, I investigate the possibility of generating all matter by physics at low energies, that may be testable at current experiments, or at those planned in the near future. One of the findings of my work is that this possibility may be realized in minimal supersymmetric extensions of the Standard Model, if some specific conditions are fulfilled. These conditions will be tested at the Tevatron collider, which is operating at the Fermilab Laboratory in the Chicago area, as well as the LHC collider at CERN, which will start operation by the end of the year 2007.

Yau W. Wah

My current research primarily focuses on the measurement of the branching ratio of a very special rare kaon decay, a k-long particle decays into a neutral pion and two neutrinos (so called the "golden" mode). This decay mode provides the cleanest and best answer to the question of CP violation in elementary particle physics that the theoretical calculation (prediction) within the so called Standard Model is unambiguous and precise. Therefore no matter what the measurement result is, standard or non-standard; it will be most fascinating.

The experimental pursuit of this measurement started in 1990 with a Chicago undergraduate, Greg Graham who wrote a senior thesis on the first measurement of this decay mode using data from a dedicated rare kaon decay (Experiment E799 at Fermilab, proposed in 1988, data taking in 1990-91). Since then, follow up experiment KTeV/E799-II (proposed 1993, data taking 1996-97 and 1999-2000) improved the limit with basically the same technique. The KTeV detector had the highest sensitivities for many decay modes that the current knowledge about neutral kaon decays are mostly from KTeV results.

Experiment E391a at KEK (Japan High Energy Accelerator Laboratory) is designed and built to measure the "golden" mode. Our group joined E391a in 2001, and is responsible to build the front-plug and back-plug calorimeters. This experiment is a pilot to get within reach of Standard Model sensitivity and also provides comprehensive background checks and understanding. Data taking will start in early 2004, and we expect many results by end of 2004. This experiment is an important step to a possible new experiment at JPARC (Japan Physics and Accelerator Research Complex, aka JHF) in 2006. This new accelerator is expected to be online in 2006.

Scott P. Wakely

My research spans a number of topics in the categories of experimental astroparticle physics and high-energy astrophysics. This includes several investigations into the nature and origin of very high energy (VHE) cosmic radiation, including gamma rays above 10 GeV and cosmic rays above 100 TeV. I am also interested in topics at the interface of cosmology and astroparticle physics, including studies of the propagation of VHE gamma rays through extragalactic photon fields. I currently am working on the following projects:

VERITAS - the Very Energetic Radiation Imaging Telescope Array System. This experiment comprises 4 12-meter imagin atmospheric Cerenkov telescopes designed to detect and measure gamma rays over an energy range of 50 GeV to 50 TeV. VERITAS is currently taking data while under construction at Kitt Peak in southern Arizona . Once complete in 2006, VERITAS will be the most sensitive instrument of its kind in the world for the investigation of gamma ray sources such as galactic supernova remnants and AGN.

TRICE - the Track-Imaging Cerenkov Detector. TRICE is a collaboration with Argonne National Laboratory to build a high-resolution imaging telescope for the measurement of Cerenkov light directly from heavy cosmic ray primaries in the atmosphere. Such a measurement has never been performed from the ground before, and would allow the determination of cosmic ray composition with unprecedented precision. Additionally,the technology developed for this task will have direct applications for the next-generation of ground-based gamma ray instruments.

Balloon and Space-based Transition Radiation Detection. Transition radiation detectors provide perhaps the only feasible way to make detailed measurements of high-energy (E > 100 TeV) cosmic ray fluxes at the top of the atmosphere. The TRD group at Chicago , which includes Professors Muller and Swordy, has recently flown two successful Long-Duration Balloon missions at the South Pole with the TRACER and CREAM instruments. In addition to this, we are working on designs for a possible future space-based TRD mission called ACCESS. ACCESS will be the largest cosmic-ray detector ever flown in space, allowing it to investigate energies up to the so-called "knee" in the primary cosmic ray spectrum.

Robert M. Wald

My research has been concerned with a broad range of topics in classical general relativity, cosmology, and quantum phenomena related to gravity. A great deal of my research has focused on the theory of black holes---regions of spacetime where gravity is so strong that nothing can escape---and the remarkable (mathematical and physical) analogy between the laws of black hole physics and the ordinary laws of thermodynamics. In particular, the fact that black holes radiate as perfect black bodies as a consequence of quantum particle creation effects has led to many deep insights into the nature of quantum gravity. My interests also span mathematical investigations of classical general relativity, and applications of general relativity to cosmology and astrophysics, such as gravitational lensing phenomena and gravitational radiation reaction effects.

In the past few years, my main research efforts have concerned the formulation of quantum field theory in the presence of gravity, i.e., quantum field theory in curved spacetime. In this approach, gravity is treated classically, but all other fields are treated in accord with the principles of quantum field theory. Some major issues of principle arise in the formulation of this theory on account of the lack of Poincare symmetry and the absence of a preferred vacuum state, but it has recently been shown that the theory can be formulated in a fully satisfactory manner. It is my hope that this will provide important clues to the formulation of a fully quantum theory of gravity itself.

Paul Wiegmann

My research focuses on the non-perturbative aspects of quantum field theory, primarily electronic systems, where interaction controls the properties of the system. This includes electronic physics in low dimensions, quantum Hall effect, and strongly correlated electronic systems. In recent works on condensed matter physics, I have concentrated on topological aspects of quantum interference.

In the area of mathematical physics, my interests include completely integrable models of quantum field theory and statistical mechanics, quantum groups, and anomalies in quantum field theory.

In recent years I have also become interested in singular behavior developing in dynamical systems.

Bruce Winstein

Most of my research had been in accelerator-based particle physics, concentrating on studying symmetries in rare kaon decays. But for the 1999-2000 academic year, I took a sabbatical at Princeton to begin to learn how to detect the cosmic microwave background radiation, particularly its polarization.

We are deep into the era where the questions in particle physics and those in cosmology are becoming ever more entwined. Indeed, while the CMB was released already 400K years after the big-bang, it contains patterns that were imprinted at a far earlier era, perhaps as early as 10-35 seconds, an era where the typical energies of particles was of order 1016 GeV, the Grand Unification (GUT) scale where we believe that all forces were unified.

My particle physics research focussed on interactions which distinguish matter and anti-matter. This work was done most recently with Professors Blucher and Wah in a Fermilab experiment called KTEV. While small violations of matter, anti-matter symmetry were discovered long ago (J. Cronin and V. Fitch, 1964), when we began KTeV it was uncertain whether that violation (CP violation) was only due to oscillations in the K, anti-K system or had a "direct" component (DCP), where the neutral Kaon and anti-Kaon decayed with different rates to pi+pi- or to pi0pi0.

We built the best electromagnetic calorimeter in the field and produced the first definitive evidence for direct CP violation. (DCP was subsequently precisely measured by a European group, by further KTeV measurements, and it has now been seen in B-meson decays.) The value we found was larger than predicted at the time but the calculations are difficult. Nevertheless, it is a confirmation of an effect predicted within the Standard Model. It is also important in that such a direct effect may very well have played a role in the early universe: the "Sakharov" mechanism for generating a matter, anti-matter asymmetry in the universe requires such an effect. Of course the magnitude of the effect we discovered in the kaon system (parts per million decay rate differences) is far too small to account for the baryon asymmetry in the universe. But science does often advance in small steps.

The KTeV collaboration has published some 50 papers and analysis continues. One particularly pretty result concerns the observation for the first time of what is called a T-odd asymmetry in a particle decay, where the final state is two charged pions and two electrons. This comes about because of the known CP violation in the kaon quantum state, but it had been difficult to see before KTeV.

After my Princeton sabbatical, I worked to establish our NSF Center for Cosmological Physics which helped me start a small group and continue working with the Princeton collaboration (which grew to include JPL and Miami). We were able to make a polarization measurement at small angular scales using just a partial data sample from our experiment (called CAPMAP) which used a 7m telescope situated at Bell Labs in New Jersey, the same site where Penzias and Wilson first detected the CMB in 1965. The full data sample is under analysis now.

The Center also seeded the QUIET (link to quiet: http://quiet.uchicago.edu/) experiment, a much more ambitious effort towards a very deep study of the CMB polarization. We are using detectors developed at JPL and will observe from Chile with two or more frequencies, to help sort out galactic foregrounds. I stepped down from being the Center director in order to fully concentrate on QUIET which has just received 3 years of funding to deploy 100 detectors; if we do well, we should be able to secure more funding for the next step of 1000 detectors, likely bringing us to a sensitivity to explore physics at the GUT scale.

Thomas A. Witten

My research concerns collective mechanisms for creating spontaneous structure in forms of conventional condensed matter such as polymer liquids, evaporating liquid drops, layer-forming surfactant micelles and thin elastic sheets. All these materials when subjected to structureless external forces develop new forms of spontaneous structure at a fine length scale, such as the sharp folds of a crumpled sheet or the thin ring stain left when a drop of dirty fluid has evaporated. These new forms of force-induced structure often arise from fundamental mechanical properties such as the competition between bending and stretching energy in an elastic sheet or between evaporative flows and capillary forces in an evaporating drop. They may arise from fundamental statistical properties such as the randomness of a chain polymer molecule or the random, tenuous structure of a colloidal aggregate. In either case the fundamental origins of the resulting structures mean that they can be used and manipulated in a wide range of material realizations independent of the specific properties of the materials.

Wendy W. Zhang

I am interested in the formation of singularities, e.g. divergences in physical quantities such as pressure, on a fluid surface due to flow and surface tension effects. Two examples are the breakup of a liquid drop and viscous entrainment. In studying how nonlinear interactions give rise to singularities, we hope to understand the kinds of simplification in dynamics that can result when a physical process involves disparate length- and time-scales. We also hope that surface tension effects can be used to create structures which span a few molecules in one dimension but are macroscopic in other dimensions. More generally, thin tendril-like structures which extend over large distances arise in many contexts and can often strongly influence the large-scale dynamics. Examples include thermal and compositional convection, Coulomb fission and the formation of tether structure on a fluid surface due to optical radiation pressure. We use analytical methods, often based on asymptotic analysis, and numerical simulations. Many of the work are inspired by, or happen in parallel with, experimental work.