Spring 2015

January 23, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Dr. Bharat Ratra, Kansas State University
Host: Prof. Irina Novikova
Title: Dark Energy: constant or time variable? (... and other open questions)
Abstract: Experiments and observations over the last decade have persuaded cosmologists that (as yet undetected) dark energy is by far the main component of the energy budget of the universe. I review a few simple dark energy models and compare their predictions to observational data, to derive dark energy model-parameter constraints and to test consistency of different data sets. I conclude with a list of open cosmological questions.

January 30, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Prof. Christine Aidala, University of Michigan
Host: Prof. W. Deconinck
Title: Spin-Momentum Correlations, Aharonov-Bohm, and Color Entanglement in Quantum Chromodynamics
Abstract: After the development of QCD in the last quarter of the 20th century, we are now in the early years of an exciting new era in which much more quantitative QCD calculations can be tested against increasingly sophisticated experimental measurements.  Advances include a greater focus on the dynamics of quarks and gluons within bound states and in the process of bound-state formation.  Over the last decade and a half, studies initially focused on spin-momentum correlations in the proton have brought to the fore several deep, fundamental issues within QCD.  We are now exploring the physical consequences of gauge invariance in QCD as a quantum field theory, analogous to the Aharonov-Bohm effects familiar to many from QED but predicted for any gauge-invariant quantum field theory.  Given the unique non-Abelian nature of the QCD gauge group, these quantum mechanical phase effects lead to an exciting novel prediction of entanglement of quarks and gluons across QCD bound states.

February 6, 2015 (Friday) 4:00-5:00p.m. Small Hall 110

Speaker: Dr. Alberto Marino, University of Oklahoma
Host: Prof. E. Mikhailov
Title: Controlling the Spatial Properties of Entangled Twin Beams
Abstract: I will present some recent work on the generation and control of highly entangled beams of light, known as twin beams.  The quantum correlations present in twin beams have recently generated great interest due to their applications in quantum information, quantum imaging, and quantum computing. In this talk I will show that non-degenerate four-wave mixing (FWM) in a rubidium vapor cell is an excellent source of continuous-variable (CV) entangled twin beams, with an intensity-difference noise of less than 13% of the corresponding classical shot-noise level.  Unlike other systems that rely on the use of a cavity, this system can support a large number of spatial modes. This leads to spatial quantum correlations and makes it possible to produce CV entangled images. I will describe some resent experiments in which we study the effect of the size and profile of the pump required for the FWM on the minimum size of the spatial correlations, or coherence area.

February 13, 2015  (Friday) 4:00-5:00p.m. Small Hall 110

Speaker:  Dr. Simona Malace, Jefferson Lab
Host: Prof. W. Deconinck
Title: The Structure of the Nucleon
Abstract: Over the past decades physicists have made dramatic progress in understanding matter in terms of its fundamental constituents and their interactions. We now think of nucleons as being made of quarks and gluons held together by the strong force. Tremendous experimental and theoretical efforts around the world lead to the emergence of a fairly viable model that describes the nucleon structure and its dynamics in terms of quark and gluon distribution functions (PDFs) and their evolution. Quantum Chromodynamics (QCD) became the theory of strong interactions. However, fully understanding the dynamical makeup of free nucleons remains still a challenge. In this talk I will emphasize ongoing theoretical and experimental efforts to extend the PDF-based description of the nucleon structure into the non-perturbative regime and to understand the phenomenon of quark-hadron duality which could become a powerful tool to probe confinement. I will also highlight plans for an upcoming experiment at Jefferson Laboratory set to answer in the most precise manner to date the fundamental question of whether the nucleon separated structure functions are modified differently by the nuclear medium. This experiment will also yield high-precision measurements for the extraction of nuclear patron distribution functions. 

February 20, 2015  (Friday) 4:00-5:00p.m. Small Hall 110
Speaker:  Dr. Alexander Balatsky "CANCELLED"
Host: Prof. E. Rossi
Title: Dirac Materials

Abstract: Recently a new single-layer material—graphene—has been discovered. This is a material where quasi-particle behavior is described by very same Dirac equation that governs behavior of relativistic particles. Dirac  fermionic spectrum leads to very unusual properties of these materials, including   Klein paradox, chirality of carriers, unusual electron transport and impurity states. These properties are not unique to graphene, instead they represent universal consequences of the Dirac spectrum of the fermionic excitation sector. I will explore these similarities with other materials exhibiting similar spectra including d-wave superconductors, superfluid 3He and recently discovered topological insulators and discuss the unique role of  symmetries that protect the Dirac spectrum. I will also discuss how we can use modern tools to design Dirac Materials and perform their quantum imaging. Iwill illustrate how the ripples in the Dirac sea produced by defects can induce fascinating features that can be probed locally.

March 6, 2015 (Friday) 4:00-5:00p.m. Small Hall 110 (cancelled due to weather)
Speaker: Prof. Mike Snow, University of Indiana
Host:  Prof. W. Deoconinck
Title: "Nuclear/Particle/Astrophysics with Slow Neutrons"
Abstract: Experiments with slow neutrons can address a number of interesting open questions in nuclear/particle/astrophysics. In this talk I will describe how slow neutrons are produced and manipulated and present a few examples of experiments in this field.  

March 27, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Christopher Monahan
Host: Prof. A. Walker
Title: Wanted: new physics
Abstract: All efforts to directly detect new fundamental particles have so far failed. Does this mean that we are really facing a nightmare scenario? The short answer - in my view is not yet. In this colloquium I will discuss a complementary approach to directly observing new particles: indirect detection. I will focus on the role that lattice quantum chromodynamics (QCD), the numerical computation of processes that are mediated by the strong force, plays in the search for new physics and discuss recent advances in this area of lattice QCD. 

April 3, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Jim Van Dam
Host: Prof. Mordijck
Title: The Scientific Challenge of Burning Plasmas
Abstract: Plasma, the so-called fourth state of matter, is pervasive throughout the universe, with many diverse scientific manifestations. The U.S. Department of Energy supports plasma science research ranging from low-temperature plasmas, high energy density plasmas, and warm dense matter, to solar, space, and astrophysical plasmas. A large research effort is also devoted to studying how high-temperature plasmas can be confined by magnetic fields in the laboratory--ultimately for the production of fusion energy. The ITER experimental facility, to be operated as an international project by a consortium of international member countries representing more than 50% of the world’s population, will push research into the frontier regime of “burning plasmas,” which are self-heated and self-sustaining. This talk will describe the unique physics characteristics of burning plasmas, illustrate some of the outstanding research opportunities in this field, and review how the U.S. and world fusion science programs have laid the foundation for taking the present step to ITER. 

April 10, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Dr. Ruth Van De Water
Host: Prof. A. Walker-Loud
Title: Modern Lattice QCD: Progress & Prospects 
Abstract: Numerical lattice-QCD simulations enable the determination of hadronic matrix elements and parameters of the QCD Lagrangian with controlled uncertainties that are systematically improvable. In the past few years, lattice methodology has been validated by comparison with a broad array of measured quantities, including some that were not yet well measured in experiment when the first good lattice calculation became available. In the coming years, numerical lattice-QCD calculations will be needed throughout the experimental high-energy physics program. After briefly introducing numerical lattice QCD, I present recent results that demonstrate the reliability of modern lattice calculations. Next I discuss the role of lattice QCD in quark-flavor physics, for which lattice QCD is already a mature tool. I finish by discussing prospects for lattice calculations needed to interpret future precision measurements as Standard-Model tests and new-physics searches. 

April 17, 2015 (Friday) 4:00-5:00p.m. Small Hall 111
Speaker: Dr. Chris Polly (Fermilab)
Host: Chris Bouchard
Title: Muon g-2 and the quest for TeV scale physics
Abstract: One of the most imperative questions in particle physics today is whether or not new physics will emerge at the few TeV scale.  Observational hints for new physics have arisen from several sectors with exciting theoretical implications that can potentially be explained by supersymmetry, dark matter, or other exotic models.  One of the most persistent hints comes from the Brookhaven muon g-2 experiment, where an ultra-precise measurement of the muon anomalous magnetic moment differs by >3 sigma from the theoretical expectation.  The anomalous magnetic moment of the muon provides a unique window into the TeV scale, and a new effort is underway at Fermilab to improve the experimental precision.  A review of the physics, the principles behind the experiment, and the incredible journey to bring the experiment to the point it is at today will be discussed.
April 24, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Dr. Jorn Randrup (Lawrence Berkeley National Laboratory)
Host: Prof. Walker-Loud
Title: Brownian Shape Evolution in Nuclear Fission
Abstract: Ever since its discovery, nuclear fission has posed challenges to our understanding of the dynamical properties of nuclear systems. The process can be regarded as an evolution of the nuclear shape, from the original compound nucleus to the two receding fragments. But even the qualitative character of this macroscopic evolution remains a somewhat contentious issue. But there is growing evidence that the nuclear shape dynamics is strongly dissipative, in which case the evolution resembles Brownian motion. Several simplifying idealizations of the theoretical treatment then suggest themselves and, as a result, nuclear fission can be described as a random walk on the multi-dimensional deformation-energy surface. This conceptually simple picture leads to a remarkably powerful tool for calculating the mass distributions of the resulting fission fragments for practically any fissionable nucleus.
May 1, 2015 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Dr. George Schwiete, Johannes Gutenberg Universität Mainz
Host: Prof. Rossi
Title: Effects of interactions on transport in disordered many-body systems
Abstract: The influence of disorder on interacting many-body systems plays a prominent role in modern condensed matter physics. Not only is the presence of disorder often unavoidable in the complex materials used in experiment, disorder leads to fascinating phenomena in their own right. Generally speaking, disorder tends to slow down the motion of particles and even very weak disorder may be sufficient to completely localize them. The addition of interactions to the problem leads to a plethora of new phenomena. In this talk, I will discuss selected examples that illustrate the rich physics of interacting disordered systems at low temperatures: In experiment, one often observes that disordered films on the verge of becoming superconducting develop a pronounced resistance maximum. I will explain our theoretical understanding of this surprising effect. Next, I intend to discuss the expansion of a cloud of bosons subjected to a disorder potential. Despite the obvious difference between these systems, an efficient theoretical approach can in both cases be based on the analysis of effective diffusion equations. This description allows to clearly identify the physical mechanisms that are relevant at low temperatures. If time allows, I will also compare charge and heat transport in the disordered electron liquid using a similar language.