Colloquia and Seminars
Colloquia and Seminars (Previous Years)
Physics and Astronomy Colloquium - Fall - 2012
(4-5 pm, Science Bldg. 127)
Precision Cosmology Through Large Surveys
Prof. Darren DePoy
Texas A&M University
Prof. Darren DePoy is currently the Rachal/Mitchell/Heep Professor and head of the Astronomical Instrumentation Lab in the Physics and Astronomy Department at Texas A&M University in College Station. Prof. DePoy received his B.S. in Physics from the Massachusetts Institute of Technology in 1982 and his Ph.D. in Astronomy from the Univ. of Hawaii in 1987. He has a long history of leading instrumentation groups at the US National Observatories, Ohio State, and Texas A&M to create new kinds of astronomical instruments for new kinds of observations. For example, DePoy built instruments and helped to organize observations for the PLANET project, which involved observations of planetary gravitational microlensing events that have detected some of the most solar-system-like planetary systems known. He is the Dark Energy Camera Project Scientist and currently works on a range of dark energy measurements. More information about Prof. DePoy and his research can be found at http://faculty.physics.tamu.edu/depoy/
The discovery of the acceleration of the Universe and "dark energy" is an exciting development in physics. I will describe the evidence for dark energy and several projects that seek to better determine key cosmological parameters that characterize this mysterious effect. I will concentrate on projects that our group is involved with and discuss some exciting future projects as well.
Neutron matter from low to high density: from cold atoms to neutron stars
Dr. Stefano Gandolfi
Los Alamos National Laboratory
Dr. Gandolfi is a scientist at Los Alamos National Laboratory (LANL) in New Mexico. He studied at University of Trento, Italy, where he earned a BA in 2003, a MA in 2004 and a PhD in physics in Nov. 2007. He was a research associate at the International School for Advanced Studies (SISSA) in Trieste Italy from 2008 to 2009, and a postdoctoral research associate at LANL from 2009 until 2011 when he was hired as a scientist in the Theoretical Nuclear/Particle/Astrophysical Group at LANL. He does theoretical research on microscopic properties of many-body systems that include cold-atoms, neutron matter and neutron stars using numerical techniques based on Monte Carlo integration
Quantum Monte Carlo methods provide an important tool to predict properties of strongly correlated systems that cannot be studied using perturbation theory. The equation of state of nuclear matter at nuclear densities is the bridge between the terrestrial experiments aiming to measure the symmetry energy and the structure of neutron stars. An even more important challenge is the study of properties of inhomogeneous neutron matter at moderate densities that is not reliable in experiments but is essential to constrain the nuclear density functionals commonly used in the physics of heavy nuclei and to study the crust of neutron stars. On the other side, low-density neutron matter exhibits important similarities to properties of strongly interacting Fermi gases that offer the important feature to be very manageable in experiments. The unitary Fermi gas is become the best tool to test the accuracy of many-body techniques that are employed in nuclear physics. In this talk I will present the recent progresses that has been made in these different fields in the last few years using Quantum Monte Carlo methods.
The Determination of the Dense Matter Equation of State from Observations of Neutron Stars
Prof. James M. Lattimer
Stony Brook University
Prof. Lattimer's research concerns the interface between astrophysics and nuclear theory: nuclear astrophysics. His main interests include the dense matter equation of state, supernovae, neutron stars, and mergers of compact stars. He received his B.S. in Physics from the University of Notre Dame and his PhD in 1976 from the University of Texas at Austin with work that indicated binary mergers involving neutron stars could be the source of the astrophysical r-process. As a postdoc at the University of Illinois, he began work on the calculation of the dense matter equation of state, which continued when he moved to Stony Brook in 1979. With his student F. D. Swesty, he developed the Lattimer-Swesty tabular equation of state which is the most-frequently used microphysics in numerical calculations of supernovae. He has also been interested in neutron star cooling, and with co-authors C.J. Pethick and M. Prakash, demonstrated the viability of the so-called direct Urca process for neutrino emission in dense matter. Together with D. Page, A. W. Steiner and M. Prakash, he found that the recently observed rapid cooling of the youngest known neutron star, in the Cas A supernova remnant, could be explained by the onset of neutron superfluidity in the star's core. He has been interested in the extraction of the nuclear equation of state from observations of neutron star masses and radii. With M. Prakash, he demonstrated an important correlation between the nuclear symmetry energy and the neutron star radius. He is a Fellow of the American Physical Society, and has received Sloan and Guggenheim Fellowships. More information about Prof. Lattimer and his research can be found at http://www.astro.sunysb.edu/lattimer/ or http://scholar.google.com/scholar?start=0&q=James+Lattimer&hl=en&as_sdt=0,44
Neutron stars are fascinating laboratories for dense matter physics. They contain the largest known magnetic fields, the highest temperature superconductors, and the densest and hottest matter apart from the early Universe. Almost three dozen neutron star masses are precisely known. Many observations can be used to estimate the radii of neutron stars. Although no one radius estimate is very precise (errors are typically at least 20\%), the ensemble of estimates can be used to limit the pressure-density relation of dense matter. Intriguingly, the collective measurements of neutron star radii are close to predictions based on nuclear data and experiments, such as nuclear binding energies, neutron skin thicknesses, giant dipole resonances, and heavy ion experiments. Furthermore, they are also consistent with recent theoretical studies of pure neutron matter. This concordance has significantly reduced the variance in predictions of the properties of supernova and neutron star mergers that will be observed in the future.
Emergence of Order in Physical, Chemical, and Biological Systems
Prof. Harry L. Swinney
Sid Richardson Regents Foundation Chair
University of Texas at Austin
(A member of the National Academy of Sciences and the American Academy of Arts and Sciences )
Dr. Swinney’s research concerns the dynamics of macroscopic systems driven far from thermodynamic equilibrium by imposed gradients. In 1975 at City College of New York, Swinney and J. P. Gollub examined flow between concentric rotating cylinders, hoping to validate Landau’s picture of the transition to turbulence as an infinite sequence of instabilities, but instead the experiments revealed an abrupt transition from doubly-periodic to chaotic behavior. In 1978 Swinney moved to the University of Texas at Austin, where experiments and numerical studies of models by his group have revealed instabilities and chaos in homogeneous chemical reactions; mechanisms that stabilize Jupiter’s Great Red Spot; chemical “Turing” patterns; spatial patterns and shock waves in granular materials; wrinkling in garbage bags and tree leaves; dynamics of gravity waves internal to the ocean; and deadly competition between bacterial colonies. Swinney co-founded and co-directs annual two-week long schools (2008-) for early career scientists in developing countries (cf. handsonresearch.org). He is a member of the National Academy of Sciences and a Fellow of the American Physical Society, the Society of Industrial and Applied Mathematics, the American Association of Science, and the American Academy of Arts and Sciences. He was awarded the Fluid Dynamics Prize of the American Physical Society, the Jurgen Moser Award of the Society of Industrial and Applied Mathematics, and the Lewis Fry Richardson Medal of the European Geosciences Union. More information about prof. Swinney and his research can be found at http://chaos.utexas.edu/people/faculty/harry-l-swinney
The emergence of patterns is one of the world’s most durable mysteries. Some patterns (clouds, zebra stripes) form in space, while others (the ebb and flow of tides, cardiac rhythms) form in time. We consider here how ordered patterns emerge in systems that are driven away from thermodynamic equilibrium by, for example, a gradient in pressure, velocity, temperature, or nutrient concentration. Although there is no general theory of pattern formation, new analysis techniques enable quantitative comparisons of patterns such as the spirals in a frog egg, a fibrillating heart, and an ocean eddy. Insight into pattern formation in diverse systems of different sizes and different underlying mechanisms can be gained from a common approach, as will be illustrated with examples from chemistry, physics, and biology.
DNA in Nanoscale Electronics
Prof. Jason Slinker
The University of Texas at Dallas
Dr. Jason Slinker, an Assistant Professor of Physics at the University of Texas at Dallas, received his PhD in Applied and Engineering Physics from Cornell University in 2007 under Professor George Malliaras. He was a postdoctoral scholar with Professor Jacqueline Barton of the California Institute of Technology (2007-2010) and joined UT Dallas in 2010. His research involves understanding and controlling the interplay between ionic and electronic charges in soft materials to produce unique electrical properties and novel device capabilities. His work with electrochemical devices includes DNA bioelectronics for nanoscale circuits and sensors and organic optoelectronic devices for energy efficiency. His efforts have led to over 30 publications with a total of over 1000 citations and three patents.
He is a member of the American Physical Society and the Materials Research Society. More information about Prof. Slinker and his research can be found at
DNA, the quintessential molecule of life, possesses a number of attractive properties for use in nanoscale circuits. Charge transport (CT) through DNA itself is of both fundamental and practical interest. Fundamentally, DNA has a unique configuration of π-stacked bases in a well ordered, double helical structure. Given its unparalleled importance to life processes and its arrangement of conjugated subunits, DNA has been a compelling target of conductivity studies. In addition, further understanding of DNA CT will elucidate the biological implications of this process and advance its use in sensing technologies. We have investigated the fundamentals of DNA CT by measuring the electrochemistry of DNA monolayers under biologically-relevant conditions. We have uncovered both fundamental kinetic parameters to distinguish between competing models of operation as well as the practical implications of DNA CT for sensing. Furthermore, we are leveraging our studies of DNA conductivity for the manufacture of nanoscale circuits. We are investigating the electrical properties and self-assembly of DNA nanowires containing artificial base pair surrogates, which can be prepared through low cost and high throughput automated DNA synthesis. This unique and economically viable approach will establish a new paradigm for the scalable manufacture of nanoscale semiconductor devices.
Accelerator Disaster Scenarios, the Unabomber, and Scientific Risks
Prof. Joseph Kapusta
University of Minnesota
Dr. Kapusta is Professor of Physics and Director of Graduate Studies at the University of Minnesota in Minneapolis. He earned a BA in 1974 at the University of Wisconsin-Madison. He earned an MA in 1976 and a PhD in 1978 at the University of California-Berkeley. He was a postdoctoral research associate at LBL, LANL and CERN before joining the faculty at Minnesota in 1982. He does theoretical research on the properties of matter and radiation at high energy-density using relativistic quantum field theory. He also does research on the anti-de Sitter/conformal field theory correspondence arising from D-branes in string theory and on the thermodynamics of nonlocal field theories arising from string theory. The physical theories of primary interest include QCD, effective hadronic field theories, electroweak theory, and nonlocal field theories. The physical environments in which they play a role include high energy nuclear collisions, the early universe, and black holes. He has published several books and more than 185 articles. He has been an Associate Editor for Physical Review since 1997. He is a Fellow of the American Physical Society and of the American Association for the Advancement of Science. More information about Prof. Kapusta and his research can be found at
The possibility that experiments at high-energy accelerators could create new forms of matter that would ultimately destroy the Earth has been considered several times in the past 35 years. One consequence of the earliest of these disaster scenarios was that the authors of a 1993 article in Physics Today who reviewed the experiments that had been carried out at the Bevalac at Lawrence Berkeley Laboratory were placed on the FBI’s Unabomber watch list. Later, concerns that experiments at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory might create mini black holes or nuggets of stable strange quark matter resulted in a flurry of articles in the popular press. These concerns were repeated a decade later before the Large Hadron Collider at CERN began operation. I discuss this history, as well as Richard A. Posner’s provocative analysis and recommendations on how to deal with such scientific risks. I conclude that better communication between scientists and nonscientists would serve to assuage unreasonable fears and focus attention on truly serious potential threats to humankind.
Semiconductor Physics in Narrow-Gap Nanostructures
Prof. Michael Santos
The University of Oklahoma
Dr. Michael Santos, Professor of Physics and Charles L. Blackburn Chair in Engineering, has been a faculty member at the University of Oklahoma since 1993. He earned a B.S. degree in Electrical Engineering and Materials Science from Cornell University (1986) and a Ph.D. degree in Electrical Engineering from Princeton University (1992). In 1992-1993, he was a postdoctoral researcher at AT&T Bell Laboratories in Holmdel, New Jersey. During a sabbatical leave in 2000-2001, he was an Invited Professor at NTT Basic Research Laboratories in Japan. He has co-authored over 200 papers on experimental semiconductor research. The main research interests of Prof. Santos are on the growth of narrow-gap semiconductors and device applications for these materials using techniques including transmission electron microscopy, reflection high-energy electron diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, high-resolution x-ray diffraction, and scanning probe microscopy. More information about Prof. Santos and his research can be found at http://www.nhn.ou.edu/faculty/santos/
There is a ceaseless demand for new materials to provide improved functionality in electronics and photonics. For example, new materials are required to improve conversion of sunlight and waste heat to electricity, broaden uses for infrared radiation, and provide alternative means of computation. The properties of semiconductors, which have traditionally been used for these applications in bulk form, can be tailored to better address specific applications by reducing one or more characteristic dimensions to the nanometer scale. Narrow-gap semiconductors, which have an energy gap of less than 1 eV, are particularly useful for high speed and infrared applications. The effective mass of electrons in InSb is two orders of magnitude smaller than the mass in free space. This property can be exploited in electronic device applications, including field-effect transistors and ballistic transport devices, where a high mobility or a long mean free path is required. The consequences of a small effective mass and large spin-orbit coupling are seen in charge transport measurements performed on structures with nanometer-scale dimensions in one or more directions. The active region of infrared lasers and detectors can be made of InAs or GaSb because a narrow gap corresponds to the energy of an infrared photon. In this talk, I will discuss collaborative projects on infrared devices, photovoltaic materials, and spin-dependent structures that rely on multilayer narrow-gap materials grown by my research group using a technique called molecular beam epitaxy.
The Dawn of the Higgs Era
Prof. Joseph M. Izen
The University of Texas at Dallas
Prof. Joe Izen received his B.S. in Physics and Mathematics, Summa Cum Laude, in June 1977 from The Cooper Union, his A.M. and Ph.D in Physics from Harvard University in 1978 and 1982, respectively. He held research and faculty positions at the University of Wisconsin at Madison and the University of Illinois at Urbana-Champaign before moving to the University of Texas at Dallas in 1991. Prof. Izen specializes in collider physics and the physics of heavy quark flavors. He is Principal Investigator of a Department of Energy – High Energy Physics grant, and he has attracted more than $5,000,000 in external funding since 1992. Currently, he collaborates on the ATLAS experiment at CERN’s Large Hadron Collider and the BABAR experiment at the Stanford Linear Accelerator Center. ATLAS is exploring the origin of mass and searching for physics beyond the standard model at the world’s highest energy proton-proton collisions. Izen works on the ATLAS Pixel detector, and his analysis interests with ATLAS include dark matter searches and quarkonium production. Prof. Izen’s interest on BABAR is the study of charmonia, charm, and exotic particles in the energy region from charm threshold to the ϒ(4S) using the radiative return from the ϒ(4S). In years past, he collaborated on the Cleo, Tasso, Aleph, Mark III, SLD, SDC, and Beijing Spectrometer (BES) experiments. Izen was the US BES Spokesperson from 1996-1997. More information about Prof. Izen and his research can be found at http://www.utdallas.edu/%7ejoe/
Photo: Prof. Izen’s group in the ATLAS Control Room, July 2012
CERN was buzzing at the start of July. Physicists on ATLAS and CMS, the two big experiments knew something, but we weren’t talking. Physics spouses made phone calls, only to learn that their friends were equally thwarted. Word that Peter Higgs was sighted in the CERN cafeteria on July 3rd spread like a wildfire. Students queued up overnight for the Higgs seminar like it was a Grateful Dead concert. On July 4th, the world learned that ATLAS and CMS had discovered a Higgs candidate with a significance of 5 standard deviations (σ). Unlike massless photons, the gauge bosons of the weak interaction are very massive; they are not made by flashlights but by accelerators like the Large Hadron Collider. Over forty-years ago Glashow, Weinberg, and Salaam developed a theory of weak interactions. The theory made extraordinary but testable predictions of a new kind neutrino scattering and a massive version of the photon. The most spectacular part of the theory was the Higgs mechanism that was invented to allow weak bosons to have mass, but incidentally predicted a new type of fundamental particle, the Higgs boson, and it explained meaning of the mass of fundamental particles like quarks and electrons. I will describe how the LHC can create Higgs bosons, how the ATLAS detector was designed to detect Higgs decays, and how ATLAS members are checking whether our 5.9 σ “Higgs-like” object is the Standard Model Higgs boson.
Energy Metabolism in Microbial Production of Fuels and Chemicals
Prof. Dongwon Choi
Texas A&M University-Commerce
Dr. DongWon Choi joined Texas A&M University – Commerce at 2010 as an￼ Assistant Professor in the Department of Biological and Environmental Sciences. He is an experienced scientific researcher in the fields of microbial physiology and environmental microbiology. He received his M.S and Ph.D. degrees in microbiology from Ball State University, Indiana and Iowa State University, Iowa, respectively. He continued his academic training as a Post-Doctoral Research Associate in the Center for Sustainable Environmental Technologies (CSET), Iowa State University. He led a team of multi-disciplinary research as the biocatalyst program manager. During his academic training, he has published 14 manuscripts in international peer-reviewed academic journals, 2 book chapters, and 13 invited presentations in various international research conferences. He also serves as Ad-hoc reviewer for peer-review international academic journals such as Energy & Fuels, Energy-The International Journal, and Biomass & Bioenergy. One of his current research focuses is the development of economically feasible bio-renewable fuel and other commodity chemical production strategy using bioenergetics control. More information about Prof. Choi and his research can be found
There has been increasing demand for the development of biorenewable fuels and commodity chemicals since we realized intrinsic problems of petroleum-based production of fuels and chemicals. The problems include 1) limited availability of crude oil resources from their natural reservoir and 2) increasing pollutants emissions from petroleum utilizing activities. Carbon dioxide is the main pollutant and raises international concern due to it’s Green House effect. However, further intensification of the Green House effect can be avoided by establishing closed loop of global carbon cycle. Energy metabolism of microorganisms can be a powerful tool to close the currently open loop of global carbon cycle while we maintain the convenience of modern, organic chemical-based life style.
Recent Research on the Thomas-Fermi Quark Model
Prof. Walter Wilcox, Baylor University
Dr. Walter Wilcox is Professor of Physics and Graduate Program Director for the Baylor University Physics Department. He earned a Ph.D. in elementary particle physics from UCLA in 1981 under the guidance of Dr. Julian Schwinger. He has also taught and done research at Oklahoma State University (1981-1983), TRIUMF Laboratory (1983-1985) and the University of Kentucky (1985-1986). He has been awarded grants from the National Science Foundation in theoretical physics, and, in collaboration with Ron Morgan, in applied mathematics. His research focuses on the development and use of numerical methods in the field of theoretical physics known as "lattice QCD". He is equally interested in teaching physics, and has had a new undergraduate quantum mechanics textbook, "Quantum Principles and Particles" (CRC Press) published this year. His Open Text Project website (http://blogs.baylor.edu/open_text/) offers many free physics teaching materials. More information about Prof. Walter Wilcox can be found at
There is a need quark models to help lead expensive lattice QCD calculations in the right directions for many-quark states where the lattice volume is still too small for accurate evaluations. I will describe a semi-classical model based upon the atomic ideas of Thomas and Fermi, but applied to quark systems. Such statistical models treat the particles as a gas at zero temperature and should become more accurate as the number of particles is increased. Although the model is designed to be most reliable for many-quark states, we find surprisingly that it may be used to fit the low energy spectrum of octet and decouplet baryons. The low energy fit allows us to investigate the six-quark doubly strange H-dibaryon state and possible 6 quark nucleon-nucleon resonances.
Optical Vortex Beams: Laser Beams with a Twist
Prof. Surendra Singh
University of Arkansas at Fayetteville
Professor Singh joined the University of Arkansas in 1982, after completing his dissertation under Professor Leonard Mandel at the University of Rochester. He has published more than 80 papers dealing with laser physics, quantum and nonlinear optics, and statistical properties of light, co-authored a graduate level textbook on Quantum Mechanics and has presented numerous contributed and invited papers/talks at national and international meetings and institutions. From 1995-2002 and 2005-2011, he served as Department Chair. He is a Fellow of the American Physical Society and a Visiting Fellow of JILA, University of Colorado. Although primarily an experimentalist, he is equally apt at theory. He has done extensive work on quantum and classical noise in lasers, and nonlinear and quantum optics. In addition to continuing his research in these areas he is exploring applications of optics to the study of nanoparticles and biopolymers. More information about Prof. Singh and his research can be found at
Laser beams are wave-like solutions of Maxwell’s equations that have finite transverse extent. In addition to linear momentum and energy, they can carry spin as well as orbital angular momentum. Most lasers, however, naturally emit the familiar Hermite-Gauss (HG) light beams that carry zero orbital angular momentum. Such laser beams have planar or spherical phase fronts. These beams can be transformed into Laguerre-Gauss (LG) family of laser beams that have twisted phase fronts. LG beams can carry nonzero orbital angular momentum and are examples of optical beams that may be described as optical vortices. Experimental realization of the transformation of HG beams into LG beams will be presented and results of interference, diffraction and polarization experiments revealing their fascinating phase and polarization properties will be discussed.
Aftermath of Stellar Explosions
Prof. Sangwook Park
The University of Texas at Arlington
Dr. Sangwook Park received his PhD in Physics from Purdue University in 1998. He was a postdoc at NASA's GSFC until 2001, and worked in Astronomy and Astrophysics Department of Penn State until 2010 as a research associate and then a senior research associate. Since August 2010, he has been an assistant professor in Physics Department of University of Texas at Arlington. Dr. Park's research interest is in the observational X-ray astronomy. His current research is mainly the study of young supernova remnants (e.g., SN 1987A, G292.0+1.8, Kepler etc), including topics of nucleosynthesis and progenitor's nature of core-collapse and Type Ia supernovae, the origins of various types of neutron stars, interstellar chemical structure, cosmic-ray acceleration etc. To perform these studies, he has been the PI on a number of guest observer programs of Chandra, XMM-Newton, and Suzaku Observatories, including three Chandra Large Projects and one Suzaku Key Project. More information about Prof. Park and his research can be found at
A supernova is the explosion of a star at the end of its life. Within ~10,000 years after the explosion, the nuclear fusion products expelled directly from interior of the progenitor star are preserved in the remnant of the supernova, which can be observed. The ambient medium in which the progenitor star had evolved is being shocked by the blast wave, and thus it is also observable. These features in supernova remnants provide an excellent opportunity to study stellar nucleosynthesis, evolution history, thermal and chemical structures of interstellar space, and the particle acceleration process, all of which cannot be performed in the laboratory. I will briefly discuss a couple of examples of the observational study of supernova remnants based on data obtained with modern X-ray space telescopes.
Optical manipulation of cells and cellular network
Prof. Samar Mohanty
University of Texas at Arlington
Prof. Samar Mohanty received his Ph.D. in Physics from India Institute of Science (IISc) in 2006. His research interests include Biophysics and Physiological studies at molecular and cellular level to whole organism. He has been leading the Biophysics and Physiology Group at University of Texas, at Arlington since 2009. Samar did postdoctoral training at Beckman Laser Institute and Medical Clinic at UC-Irvine. Prior to this, he has worked as a scientist in Center for Advanced Technology and has carried out biophotonics research in India, Germany, Italy, UK and Singapore. He is using novel photonics technologies for manipulating and imaging molecular and cellular processes from single molecule to whole organism level. He has several patents and nearly 100 publications in journals and edited volumes and has co-founded several startup companies. He has won several awards including Robert S. Hyer award by TX section of APS in 2011. Samar is actively involved in biophotonics education as SPIE senior member and visiting lecturer, member of editorial advisory board of journal, chair of international conference, SPIE chapter-advisor and educational board member of Biophysical society. More information about Prof. Samar Mohanty and his research can be found at
I will introduce recent developments on manipulating cellular systems at micro/nanoscopic level using optical methods and simultaneous probing of structural/functional changes using multimodal microscopy. The unique multimodal imaging and manipulation platform developed in our lab allows multiphoton excitation, digital holographic imaging, atomic force microscopy, total internal reflection fluorescence excitation, near-field scanning optical microscopy, epifluorescence and phase contrast imaging, integrated with optical tweezers, laser spanner, optical stretcher and laser scissors. I will describe recent introduction of fiber-optic tweezers, scissors, and rotator for manipulation and characterization of microscopic objects at large depths. Further, to widen the influence of photons on cellular network without compromising the cellular specificity, the interaction (photothermal, photochemical and photomechanical) of photons with cells, was enhanced by use of suitable probes. I will briefly describe recent use of these hybrid optical methods for (i) axonal guidance, (ii) drugs and gene delivery into cells and (iii) highly-effective stimulation for modulating neuronal functions.