1. Quantum Gravity with Anisotropic Scaling and the Multicritical Universe

    01:21:23

    from UK College of Arts & Sciences / Added

    18 Plays / / 0 Comments

    Dr. Petr Horava University of California, Berkeley The problem of understanding how gravity fits together with other fundamental interactions of matter has been at the forefront of theoretical research for many decades, leading to the rich framework of string theory and M-theory. In this framework, many fundamental questions are being resolved, but many remain quite mysterious, suggesting that some novel concepts may be needed. I review the recent concept of multicritical gravity with Lifshitz-type anisotropic scaling, and its applications in areas ranging from particle phenomenology beyond the standard model to non-relativistic versions of the AdS/CFT correspondence.

    + More details
    • The Astrophysics of Black Hole Spin

      01:10:46

      from UK College of Arts & Sciences / Added

      18 Plays / / 0 Comments

      Dr. Reynolds University of Maryland In addition to providing vital clues as to the formation and evolution of black holes, the spin of black holes may be an important energy source in the Universe. Over the past couple of years, tremendous progress has been made in the realm of observational measurements of spin. I will describe these efforts with particular focus on the use of X-ray spectroscopy to probe the spin of supermassive black holes in active galactic nuclei (AGN). For the first time, we are obtaining hints about the distribution of spins across the population of supermassive black holes with some interesting and unexpected consequences. After discussing spin, I will also address questions related to the driving of relativistic jets from AGN and the jet-disk connection. I shall conclude by discussing future prospects enabled by Astro-H (to be launched in 2015) and LOFT/ATHENA+ (currently under consideration by ESA).

      + More details
      • Cosmic Linear Accelerators: Extreme Reconnection and other Surprises from the Crab Nebula

        01:11:43

        from UK College of Arts & Sciences / Added

        16 Plays / / 0 Comments

        The unexpected discovery of gamma-ray flares from the Crab Nebula may have surprising implications for plasma astrophysics. Standard particle acceleration mechanisms cannot account for the energies of the flaring photons. Instead, these observations point toward an acceleration process involving rapid destruction of magnetic field through reconnection. I will discuss the extreme particle acceleration process that may lead to the flares, and the likely role of current-driven instabilities in triggering reconnection in the Crab and elsewhere.

        + More details
        • Topological Phases in Correlated Materials

          01:11:53

          from UK College of Arts & Sciences / Added

          16 Plays / / 0 Comments

          Dr. Yong-Baek Kim University of Toronto Recently there have been significant theoretical and experimental efforts to understand and identify the so-called topological phases of matter in interacting electron systems. These topological phases may be characterized by different kinds of topological properties such as non-trivial edge/surface states and/or unusual elementary excitations in the bulk or surface. Notable examples include quantum spin liquids, topological insulators, and other closely related phases. One of the main challenges is to come up with theoretical criteria that can be used to identify or predict correlated materials that hold promise for the emergence of such topological phases. We discuss recent theoretical and experimental developments in this direction, along with a brief introduction to some of the proposed topological phases. In particular, we focus on correlated materials with strong spin-orbit coupling and/or near a metal-insulator transition.

          + More details
          • In Pursuit of Dark Matter: Recent Results from the Super CDMS Program

            01:08:11

            from UK College of Arts & Sciences / Added

            16 Plays / / 0 Comments

            Dr. Jodi Cooley Southern Methodist University

            + More details
            • Alfred Shapere

              32:54

              from UK College of Arts & Sciences / Added

              16 Plays / / 0 Comments

              Alfred Shapere presenting at Great Lakes String 2013

              + More details
              • Nicolas Regnault

                28:51

                from UK College of Arts & Sciences / Added

                15 Plays / / 0 Comments

                Nicolas Regnault presenting at the Great Lakes Strings 2013.

                + More details
                • Gauge fields with cold atoms

                  01:32:01

                  from UK College of Arts & Sciences / Added

                  15 Plays / / 0 Comments

                  Gauge fields are ubiquitous in Physics. For example, in the context of high energy physics, they are the fundamental carrier of forces; while in condensed matter systems the associated physical fields (electrical and magnetic) are essential in creating and understanding many-body phenomena. Here I present our experimental work synthesizing static gauge fields for ultracold neutral atoms (bosonic and fermionic alkali atoms), analogous to applied fields in condensed matter systems. I will discuss these static gauge fields in the language of spin-orbit coupling where it consists of an equal sum of Rashba and Dresselhaus couplings. In experiment, we couple two internal states of our alkali atoms with a pair of ``Raman'' lasers and load our degenerate quantum gas into the resulting adiabatic eigenstates. For a Bose gas, a function of the Raman laser strength, a new exchange-driven interaction between the two dressed spins develops, which drives a (quantum) phase transition from a state where the two dressed spin states spatially mix, to one where they phase separate. Going beyond this simple modification to the spin-dependent interaction, we show that in the limit of large laser intensity, the particles act as free atoms, but interact with contributions from higher even partial waves.

                  + More details
                  • The Proton's Weak Charge

                    53:33

                    from UK College of Arts & Sciences / Added

                    15 Plays / / 0 Comments

                    Dr. David Armstrong College of William and Mary The Proton's Weak Charge One of the highest priorities of present-day experimental particle and nuclear physics is to search for indications of physics which is not contained in the Standard Model. Precision measurements of quantities that are robustly predicted within the Standard Model are an important class of such searches. An example is a measurement of the proton's weak charge. The weak charge is the strength of the proton's vector coupling to the weak neutral current, and its value is a firm prediction of the Standard Model. Thus an experimental test of the prediction is well motivated as a search for new physics. A recently completed experiment at Jefferson Lab, Qweak, has the goal of making the first precision measurement of the weak charge, using parity-violating electron scattering from hydrogen at very low momentum transfer. The result from the first subset of data will be presented, as well as an overview of the data analysis for the full data set and prospects for the final result, which will provide a sensitivity to new physics at the multi-TeV scale.

                    + More details
                    • Defects with Character: Majorana Local Modes in Condensed-Matter Systems

                      01:13:53

                      from UK College of Arts & Sciences / Added

                      15 Plays / / 0 Comments

                      Dr. Bertrand Halperin Harvard University Theory predicts the existence of some peculiar phases of quantum condensed matter systems that have multiple degrees of freedom with very low energy, when localized “defects” are introduced. I shall focus on a class of these phases where each defect has half of a conventional degree of freedom, and the defects may be considered as sites for localized zero-energy states of a “Majorana fermion”. Such defects would also exhibit the intriguing property of “non-Abelian statistics” -- i.e., if various defects can be moved around each other, or if two identical defects can be interchanged, the result is a unitary transformation on the quantum mechanical state that depends on the order in which operations are performed but is insensitive to many other details. In my talk, I will try to explain these various concepts and discuss the attempts to realize them in condensed matter systems.

                      + More details

                      What are Tags?

                      Tags

                      Tags are keywords that describe videos. For example, a video of your Hawaiian vacation might be tagged with "Hawaii," "beach," "surfing," and "sunburn."