The 2016 Nobel Prize in Physics was awarded to David Thouless, John Kosterlitz, and Duncan Haldane for research broadly associated with topology in condensed matter physics. In the first half of the talk I  will describe the two-dimensional XY model which undergoes a Berezinskii-Kosterlitz-Thouless phase transition. This transition, unlike many magnetic transitions, lacks spontaneous symmetry-breaking and is driven by the proliferation of topological excitations, vortices. The analog of of this excitation in three dimensions is the "hedgehog" of the Heisenberg magnet. I will explain what this has to do with quantum phase transitions of the two-dimensional Heisenberg antiferromagnet, explicated by Haldane.

I will give a synopsis on Quantum Chromodynamics (QCD) — the fundamental theory of strong interaction, and some of its consequences.
Lattice gauge theory is introduced as a practical way of solving the theory through computer simulation with Monte Carlo methods.
I will show how the proton mass and spin are divided into their quark and glue components in lattice QCD calculations.

Exotic hidden charm pentaquarks were discovered by the LHCb Collaboration in summer 2015. I discuss  two interpretations of these  newly discovered particles. In the QCD inspired hadrocharmonium approach pentaquarks arise naturally as bound states of quarkonia excitations and ordinary baryons. Decay width of the P_c(4450) LHCb pentaquark is explained and calculated, masses and quantum numbers of new pentaquarks are predicted.  In another approach pentaquarks are interpreted as molecular-type loosely bound  states of hadrons with  open charm. Binding in this model is due to the one-pion exchange and interplay of partial waves with different angular momenta.  The hadroquarkonium and molecular approaches  to exotic hadrons are compared and their relative advantages and drawbacks are discussed.

Over the past 25 years, it has been recognized that the light element carbon plays a crucial role in the early chemical enrichment of the Universe.  One fundamental observation is that the frequency of the so-called carbon-enhanced metal-poor (CEMP) stars in the Milky Way increases dramatically with decreasing iron abundance – from 20% of all stars with [Fe/H] < -2.0 to > 80% of stars with [Fe/H] < -4.0.    Recent discoveries of enhanced carbon in damped Lyman alpha systems at high redshift reveal that the abundance patterns observed in this gas are commensurate with a sub-class of the CEMP stars, the so-called CEMP-no stars, which exhibit little or no enhancement of their neutron-capture elements – providing one of the first direct observational linkages between the high-z Universe and presently observed stars in the Galaxy.  I summarize recent progress on our understanding of the production of carbon by first-generation stars, and the powerful constraints that this information provides on Galactic chemical evolution models, the initial mass function in the early Universe, and the nature of first-star nucleosynthesis.

String theory was originally invented to describe hadrons, but soon after Quantum Chromodynamics (QCD) emerged as the precise theory of the strong nuclear force. A quarter century later it was understood that string theory and certain gauge theories akin to QCD are in fact different descriptions of the same physics. I will review the basic relations between gauge theories and strings, and will motivate the exact gauge/string dualities by studying coincident D-branes. I will also discuss applications of these ideas to theories at finite temperature and to gauge theories which exhibit color confinement. The colloquium will also cover some of the recent progress, including the quantum entanglement entropy and three-dimensional conformal field theory.

This is the 2016 Chamblin Colloquium, in memory of our colleague Andrew Chamblin of the University of Louisville.  There will be a special reception beginning at 3pm in CP179.

Neutrinos have come a long way in the human endeavor from their days as a ``desperate remedy.''  Their study now forms the cornerstone of the high energy physics program in the United States.  The U.S. will play host to an international project called DUNE which will explore many of the most important open questions in neutrino physics.  We discovered neutrino mass by doing long-distance quantum phase interferometry with large detectors that were both sensitive scientific instruments and exquisitely beautiful devices.  DUNE will employ an enormous liquid argon time-projection chamber to make the most thorough measurements of neutrino oscillation phenomena ever undertaken.  The large far detector will enable the exploration of a plethora of physical phenomena including nucleon decay and dark matter.  After briefly discussing the history of neutrinos, I will describe the measurements we will make with DUNE and some physics opportunities we will have along the way.

Supermassive Black Holes (SMBHs) are ubiquitous in the contemporary universe.

But when and where did they form? Recent discovery of quasars hosting SMBHs

more massive than a billion solar masses at redshifts z > 7, when the universe

was less than 700 Megayear old, provides a substantial challenge to current

paradigm of a hierarchical structure formation, which tells us that massive objects

form late in the history. In my talk, I will discuss the latest progress (in) and our

contribution to understanding of formation of these most enigmatic objects.

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Oxide materials are the most abundant compound in the earth’s crust and possess a wide range of electrical, optical, and magnetic properties. For instance, insulators, high quality metals, dielectrics, ferroelectrics, piezoelectrics, semiconductors, ferromagnetics, transparent conductors, superconductors, and nonlinear optic materials have all been produced using oxide materials. Oxide materials have enormous potential, particularly as the fundamental building block of a new generation of electronic devices. We create these materials by artificially layering various atoms including oxygen at the single atomic level and discovering novel properties that are likely to find applications in electronic, magnetic, optical and electromechanical devices. I will discuss how our research [1-6] played a role in understanding the fundamental solid state phenomena at the atomic scale and the discovery of new materials so that we can use them to develop new oxide nanoelectronic devices. Atomic layer control of novel oxide heterointerfaces may provide some of the answers that we need to continue the electronics revolution, particularly for nanoscale devices with new functionality that are currently being developed and can be applied to various fields.

1. “Polar Metals by Geometric Design”, Nature 533, 68 (2016)

2. “Emergence of Room-temperature Ferroelectricity at Reduced Dimensions” Science, 349, 1314 (2015)

3. “Giant piezoelectricity on Si for hyper-active MEMS” Science, 334, 958 (2011)

4. “Metallic and insulating oxide interfaces controlled by electronic correlations” Science, 331, 886 (2011)

5. “Creation of a two-dimensional electron gas at an oxide interface grown on silicon” Nature Communications, 1, 94 (2010)

6. “Ferroelastic switching for nanoscale nonvolatile magnetoelectric devices” Nature Materials, 9, 309 (2010)

The OMC1 BN/KL outflow, located immediately behind the Orion Nebula, may have been triggered

by the dynamic decay of a non-hierarchical system of massive stars that resulted in the formation of a

compact, AU-scale binary, or more likely, a protostellar merger (Bally et al. 2011, 2015). The event

ejected the ∼ 20 M binary or merger remnant (suspected to be radio source I), the ∼12 Solar-mass

BN object, and infrared source n, and released more than 1048 ergs of energy about 500 years ago.

I will present ALMA observations of CO and the continuum with 1" angular resolution and multi-

conjugate adaptive optics images at 0.06" resolution in the 2.12 μm H2 and 1.64 μm [FeII] emission

lines. Explosive outflows similar to Orion may be associated with the ejection of runaway stars, the

production of IR-flares with luminosities between novae and supernovae, and have profound feedback

impact on their parent molecular clouds. Massive protostars accreting at high rates develop AU-scale

photospheres that resemble red supergiants. Protostellar mergers may be relatively common in massive

star forming regions because of the large cross-sections of bloated massive protostars, the high stellar

volume density of forming clusters, and the dissipative nature of dense cloud cores and clumps.

References:

Bally, J., Ginsburg, A., Silvia, D., et al. 2015, A&A, 579, 130

Bally, J., Cunningham, N. J., Moeckel, N., et al. 2011, ApJ, 727, 113

 

Astrometric observations tell us that the matter content of the Universe is dominated by dark matter, a quantity that finds no explanation within the Standard Model of particle interactions. Moreover, popular theories that would explain dark matter in terms of new, high-energy physics have as yet no empirical support from studies at high energy colliders. It is possible, rather, that essential clues as to its nature may first come from the appearance of light, weakly coupled new physics, to which low-energy, precision tests of the Standard Model are exquisitely sensitive. In this context, I will discuss an experimental anomaly in $^8$Be nuclear transitions that may be interpreted as evidence for a new, weak force of some 12 fm in range. I will review the experimental evidence, its interpretation and implications, and emphasize what further experimental tests can be done to probe the experimental anomaly and its interpretation.