1. Colloquium: Cosmological Implications of Recent Low-noise, High-resolution Measurements of the Cosmic Microwave Background

    01:07:49

    from UK College of Arts & Sciences / Added

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    Dr. Lloyd Knox University of California, Davis Observing the sky in the microwave region of the spectrum allows us to directly image the universe when it was just a few hundred thousand years old. The universe was much simpler then, simple enough that its expected statistical properties, given a model, can be calculated with high accuracy. Recent improvements in measurement resolution and sensitivity, most notably from the Planck satellite, but also from the South Pole Telescope, have provided precision tests of the standard cosmological model. In this colloquium I will introduce the cosmic microwave background (CMB) and the standard cosmological model. I will explain the nature of these precision tests and what we are learning about the origin of all structure in the universe, and about the background of neutrinos thermally produced in the big bang. I will also cover how the improvements in resolution and sensitivity are opening up a new window on the dark universe, via gravitational lensing of the CMB.

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    • Colloquium: Discovery of a North-South Asymmetry in the Distribution of Local Stars and its Implications

      01:10:33

      from UK College of Arts & Sciences / Added

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      Studies which would try to fix the local dark matter density through observations of the nearby stars invariably assume that the stars are in gravitational equilibrium. In recent years, however, it has become clear that the Milky Way displays many transient phenomena; it is a much more violent place than earlier thought. I will show how observations of the local solar neighborhood from the Sloan Digitial Sky Survey can probe the vertical equilibrium of the Galactic disk, by testing the symmetries present in the stars' distribution. Our analysis reveals a failure of north-south symmetry with respect to the galactic plane and thus that vertical equilibrium is wanting. I will consider our result in light of other observational studies, suggest further observational tests, and finally offer a perspective on its implications for dark-matter direct detection experiments.

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      • Colloquium: Glimpsing Color in the World of Black and White

        01:08:04

        from UK College of Arts & Sciences / Added

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        Glimpsing color in a world of black and white Protons, neutrons and all the many other strongly interacting subnuclear particles, known as hadrons, are made of quarks and gluons. These fundamental constituents are held together by a color force described by quantum chromodynamics (QCD). A detailed understanding of how the strong coupling regime of QCD, which is responsible for confinement and dynamical chiral symmetry breaking, determines the spectrum and structure of hadrons will be outlined. Such studies, both experimental and theoretical, color in the picture of strong dynamics. What we know now and the glimpses to come from accelerator facilities like that at Jefferson Lab will be described.

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        • Colloquium: New Dialogues: Entanglement, Holography & Renormalization

          01:15:12

          from UK College of Arts & Sciences / Added

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          In science, we often see new advances and deep insights emerging from the collision or intersection of what appeared to be separate research areas. The theme of my colloquium will be an ongoing collision between the three ideas listed in my title which has been generating interesting new insights into a variety of fields, eg, condensed matter physics, quantum field theory and even quantum gravity. I will give an introduction to each of these three ideas separately and then discuss the intersections that have been generating new insights in recent years. Speaker/Presenter: Robert Myers, Perimeter Institute for Theoretical Physics

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          • Colloquium: Organic (Plastic!) Semiconductors

            01:16:31

            from UK College of Arts & Sciences / Added

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            Organic materials are finding an increasing number of possible niches in electronic devices. I will give a very brief overview of some of the present and anticipated applications of organic semiconductors and issues in understanding their application. I will then discuss some of our recent experiments on using infrared electro-optics to measure the mobility of charges in organic thin-film transistors and conclude by describing our ongoing experiments to measure the thermal conductivities of organic semiconductors, important for possible applications as thermoelectric power generators. Speaker / Presenter: Joseph Brill, Dept of Physics & Astronomy, University of Kentucky

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            • 2013 Colloquium: Quantum Criticality in Spin Systems

              01:32:01

              from UK College of Arts & Sciences / Added

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              Close to the absolute zero of temperature, when pushed to the edge between two phases of matter, simple lattice Hamiltonians of spins can display the incredibly rich phenomena of "quantum criticality". Quantum critical ground states are described by the most complex wavefunctions known to physicists, yet they can be categorized by "universality classes" that are independent of the details of the Hamiltonians that realize them. In this colloquium I will show how such quantum critical spin systems can arise in real-world materials, and explain our successes in developing quantum many-body simulations of a new universality class of deconfined quantum critical points.

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              • Colloquium: The Future of the Sloan Digital Sky Survey

                01:07:01

                from UK College of Arts & Sciences / Added

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                I describe plans for the next-generation Sloan Digital Sky Survey, to begin in July 2014, and which consists of three programs, APOGEE-2, MaNGA and eBOSS. APOGEE-2 will use both the Sloan Foundation Telescope at Apache Point and the du Pont Telescope at Las Campanas to study Galactic archaeology with high-resolution near-infrared spectroscopy. MaNGA will develop fiber bundle technology for the BOSS spectrograph to perform multiplexed spatially resolved spectroscopy with an unprecedented combination of wavelength coverage and resolution for 10,000 nearby galaxies. eBOSS will study the Universe�s expansion using a massive survey of galaxies and quasars. eBOSS will also perform follow-up spectroscopy on X-ray and variable sources, making it both the largest and most broadly selected quasar survey. I will show how this innovative set of programs will lead to a better understanding of cosmology and galaxy formation, as well as stellar and exoplanetary astronomy. Speaker / Presenter: Michael Blanton, Dept of Physics, New York University

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                • Colloquium: Topological Surface States in Topological Insulators, Superconductors and Beyond

                  01:11:29

                  from UK College of Arts & Sciences / Added

                  153 Plays / / 0 Comments

                  Topological Surface States in Topological Insulators, Superconductors and Beyond M Zahid Hasan, Dept of Physics, Princeton University Bulk Topological Insulators are a new phase of electronic matter which realizes a non-quantum-Hall-like topological state in the bulk matter and unlike the quantum Hall liquids can be turned into superconductors. In this talk, I will first review the basic theory of topological matter and experimental probes that reveal topological order. I will discuss experimental results that demonstrate the fundamental properties of topological insulators such as spin-momentum locking, non-trivial Berry’s phases, mirror Chern number, absence of backscattering or no U-turn rule, protection by time-reversal symmetry and the existence of room temperature topological order (at the level of M.Z.H and C.L. Kane, Rev. of Mod. Phys., 82, 3045 (2010)). I will then discuss the possible exotic roles of broken symmetry phases such as superconductivity and magnetism in doped topological insulators and their potential device applications in connection to our recent results as well as outline the emerging research frontiers of the field as a whole. Time permitting, I will also present experimental results on a new class of topological insulators beyond the Kane-Mele Z2 theory.

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                  • Colloquium: Viscosity, Quark Gluon Plasma, and String Theory

                    01:08:21

                    from UK College of Arts & Sciences / Added

                    55 Plays / / 0 Comments

                    Viscosity, quark gluon plasma, and string theory Viscosity is a very old concept which was introduced to physics by Navier in the 19th century. However, in strongly coupled systems, viscosity is difficult to compute from first principle. In this talk I will describe some recent surprising developments in string theory which allow one to compute the viscosity for a class of strongly interacting quantum fluids not too dissimilar to the quark gluon plasma. I will describe efforts to measure the viscosity and other physical properties of the quark gluon plasma created in relativistic heavy ion collisions.

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                    • Controlled Magnetic Reversal and Emergent Metamagnetism in Permalloy Films Patterned into Artificial Quasicrystals

                      01:11:31

                      from UK College of Arts & Sciences / Added

                      53 Plays / / 0 Comments

                      Dr. Lance Delong University of Kentucky Ferromagnetic (FM) thin films patterned into periodic lattices of nanoscale holes or dots are candidated for UHD data storage media, an drelated wire network patterns are of fundamental interest as examples of controlled phase transitions in "artificial spin ice". Our recent Physical Review Letter reported an experimental study of the static and dynamic magnetic properties of FM permalloy thin films patterned as Penrose P2 (quasicrystal) tilings that exhibit long-range order, but aperiodic translational symmetry. Our DC magnetization and ferromagnetic resonance data constitute, we believe, the first experimental study of th espin wave dynamics of an artificial FM quasicrystalline thin film. Ground-breaking efforts were required to both pattern and deposit the sample film materials, and to execute large-scale numerical simulations of their static and dynamic behavior. This work demonstrates a new method for controlling the evolution of FM domain walls and spin wave spectra in magnetic media, in spite of a lack of periodic symmetry in an artificial quasicrystalline pattern. Simulations reveal a remarkably controlled sequence of reversals of individual film segments located on sublattices of the quasicrystal pattern, which may signal the occurence of true metamagnetic phase transitions in larger-area samples. These results directly imply FM films patterned as Penrose P2 tilings constitute a novel class of magnonic crystals whose magnon frequency dispersion and physical properties were heretofore unknown.

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