Colloquia 2017 Spring

  • 1/12/17
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  • 1/19/17
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  • 1/26/17
    • Speaker Joseph Formaggio
    • Affiliation MIT
    • Title Weighing neutrinos
    • Abstract The mass of the neutrino has been an elusive quantity physicists have tried to
      measure since the very inception of the particle. The most sensitive direct
      method to establish the absolute neutrino mass is observation of the endpoint of
      the tritium beta-decay spectrum. A lower bound for the (effective) electron
      neutrino mass of 9(0.1) meV is set by observations of neutrino oscillations, while
      the KATRIN Experiment -- the current-generation tritium beta-decay experiment
      that is based on Magnetic Adiabatic Collimation with an Electrostatic (MAC-E)
      filter -- will achieve a sensitivity of around 0.2 eV. Project 8 is a new experiment
      that uses Cyclotron Radiation Emission Spectroscopy (CRES) with the potential
      to probe much of the unexplored neutrino mass range with sub-eV resolution. In
      this talk, I will review the current status of these two experiments (KATRIN and
      Project 8) as they seek to finally measure the mass of the neutrino.
  • 2/2/17
    • Speaker Crystal Bailey
    • Affiliation APS
    • Title Breaking the Myth of the "Non-Traditional" Physicist: The Real Story About Employment for Physics Graduates
    • Abstract

      Physics degree holders are among the most employable in the world, often doing everything from managing a research lab at a multi-million dollar corporation, to developing solutions to global problems in their own small startups. Science and Technology employers know that with a physics training, a potential hire has acquired a broad problem-solving skill set that translates to almost any environment, as well as an ability to be self-guided and -motivated so that they can teach themselves whatever is needed to be successful at achieving their goals. Therefore it's no surprise that the majority of physics graduates find employment in private--sector, industrial settings. At the same time, only about 25% of graduating PhDs will take a permanent faculty position--yet academic careers are usually the only track to which students are exposed while earning their degrees.

      In this talk, I will explore less-familiar (but more common!) career paths for physics graduates, and will provide information on resources to boost yourcareer planning and job hunting skills.

  • 2/9/17
    • Speaker Rahul Nandkishore
    • Affiliation Colorado
    • Title Many body localization and thermalization
    • Abstract I will provide an overview of recent developments in the non-equilibrium statistical mechanics of isolated quantum systems. I will provide a brief introduction to quantum thermalization, paying particular attention to the `Eigenstate Thermalization Hypothesis' (ETH). I will then discuss a class of systems which fail to quantum thermalize and whose eigenstates violate the ETH: These are the many-body localized systems; their long-time properties are not captured by the conventional ensembles of quantum statistical mechanics. These systems can locally remember forever information about their local initial conditions, and are thus of interest for possibilities of storing quantum information. I will discuss some insights that have emerged from the study of many body localization, including a new form of emergent quantum integrability that is robust to arbitrary perturbations, and the discovery of new dynamical phases of matter with no analog in thermal equilibrium.
  • 2/16/17
    • Speaker  Gabriella Sciolla        
    • Affiliation  Brandeis
    • Title  From Elementary Particles to the Cosmos: Searching for Dark Matter at the LHC
    • Abstract Five decades of astronomy and cosmology have provided convincing evidence that 85% of the Universe is made of Dark Matter. While a lot is known about the amount and distribution of Dark Matter, its particle nature remains unknown. The Large Hadron Collider (LHC) can help shed light on this mystery. In this talk, I will discuss how we look for Dark Matter at the LHC and the status of our searches with the ATLAS and CMS experiments.
  • 2/23/17
    • Speaker  Anthony Mezzacappa  
    • Affiliation UT and ORNL 
    • Title     From Stars to Nuclei and Back: Our Cosmic Origin and the Exascale Challenge to Find It 
    • Abstract We learn in elementary school that the elements in the Periodic Table are the building blocks of our world, including our very bodies. But from where do the elements come? This is among the most basic questions we can ask, yet the precise answer remains in front of us. We witness the cycle of life in our daily lives, everywhere on Earth. This is no less true in the Universe. With the exception of the lightest elements such as hydrogen and helium, elements are made in stars. As stars evolve and die, these elements pepper the interstellar medium, from which new stars, and planets, – in particular, our solar system – form. We understand the essential elements of this cycle – from stellar birth, life, and death, to the formation of the elements, to the formation of new stars and planets including those elements, to ultimately the origin of our solar system and life on Earth given those elements. But pieces of the puzzle are missing. We do not yet fully understand how certain stars that are factories for many of the elements, die, nor do we know the precise origin of half the elements heavier than iron, although we have narrowed down the list of possible sites. Today’s colloquium will focus on the death of massive stars in catastrophic explosions known as core collapse supernovae. Such supernovae provide the lion’s share of the elements between oxygen and iron, and are considered a potential site for the origin of half the elements heavier than iron. Arguably, they are among the most important sources of elements in the Universe. Such supernovae present us with a general relativistic, radiation magnetohydrodynamic – i.e., a multi-physics – environment to model. Further richness and complexity is added by the fact that the macroscopic evolution of such a system is governed in no small part by the high-density, neutron-rich, nuclear matter at the core of the supernova and by the microscopic interaction of radiation in the form of neutrinos with this stellar core nuclear material. I will discuss specific examples of how the macroscopic and microscopic worlds intertwine to produce such a supernova. It is intuitively obvious that such a multi-physics arena might wind up among the set of exascale challenges that must be met in order to advance our understanding of the world and our ability to use it for the common good. Indeed, as I will discuss, core collapse supernovae do in fact present us with a sustained exascale challenge. I will provide concrete examples to illustrate why. The cost to meet such a challenge, in human effort and in the provisioning of leadership-class computing platforms and their use, is high, but the scientific return on investment is significant. Progress, particularly within the past decade, has been rapid. A new and related branch of astronomy – gravitational wave astronomy – has recently been born. We are beginning to see the goal. We stand on a foundation of accumulating knowledge and experience. And we are provided with ever-more-capable computational and observational instruments as we endeavor to reach that goal. These are exciting times to be a core collapse supernova modeler, and I look forward to sharing my excitement with you.
  • 3/2/17
    • Speaker  James T. Linnemann
    • Affiliation  Michigan State University
    • Title HAWC - Extreme Astronomy with Big Buckets of Water

      Abstract Though we can see thousands of stars in a clear night sky, the number of known sources emitting TeV gamma rays is less than 200.  This is both because there are few instruments capable of measuring such photons, and because the sources of such photons are restricted to particularly violent astrophysical processes.  The HAWC (High Energy Water Cherenkov) array is the only survey instrument in this energy range.  Located on a plateau between two volcanos in Mexico at an altitude of 4100 m, HAWC is able to survey 60% of the sky, and observes 1/6 of the full sky at any moment, day or night.  The HAWC array was commissioned in March 2015.  I will discuss the array, its construction and principles of operation, results from the first year of running, and how we are pursuing multi-messenger astronomy to better understand the nature of TeV gamma ray sources.

  • 3/9/17
    • Speaker ​Alex Seidel    
    • Affiliation  Washington University​​​​​​ 
    • Title Topological quantum spin liquids
    • Abstract The phenomenon of symmetry breaking is ubiquitous in physics, and is the main reason why much of the world surrounding us is classical: Many microscopic degrees of freedom are locked in place with respect to one and other, such that their collective motion can be described classically. Due to its universality and ubiquity, the concept of a broken symmetry has also been a major ground for cross-fertilization between condensed matter and high energy physics.
      This success is remarkable since experience with finite quantum systems only teaches that there is no such thing as broken symmetry. This is due to the phenomenon of quantum zero point motion, which tends to restore symmetry even at T=0. The fact that symmetry breaking is so prevalent in infinite (or very large) quantum systems is thus stunning, and renders certain aspect of many quantum states of matter more classical than one has any right to expect.
      The field of quantum anti-ferromagnetism has played a paradigm defining role in shaping our understanding of broken symmetry. The field went from strong theoretical bias against symmetry breaking (including even Landau(!)) to a strong bias in favor of it (Neel, van Vleck), till eventually, the idea of a symmetry-unbroken quantum "spin liquid" enjoyed a renaissance (Anderson).
      While originally, the spin liquid idea drew its inspiration from a theory for a "different" metallic state, with historical roots in quantum chemistry (Pauling), it is viewed today as one of several viable avenues to a so-called "topologically ordered phase". Both experimentally and theoretically, however, the possibility for a topological spin liquid has remained in question for decades. This talk will report significant progress on the theoretical side, after reviewing the historical developments sketched above.
  • 3/16/17
    • Spring Break
  • 3/23/17
    • Speaker  Sally Dawson
    • Affiliation  BNL
    • Title  Physics after the Higgs
    • Abstract With the discovery of the Higgs boson in 2012, particle physics entered a new
      era of discovery.  There are many crucial questions to be answered.  Is this particle
      the Higgs boson predicted by the Standard Model?  Does it have anything to do with dark matter?  Are there more Higgs bosons?  Uncovering the precise properties of the observed particle and searching for possible heavy scalar Higgs -like particles will be a major focus of particle physics in the coming years.
  • 3/30/17
    • Speaker Lara Perez-Felkner
    • Affiliation FSU
    • Title TBA
    • Abstract
  • 4/6/17
    • Poster Session
  • 4/13/17
    • Awards Ceremony
  • 4/20/17
    • Speaker David Norris
    • Affiliation ETH Zurich
    • Title TBA
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  • 4/27/17
    • Speaker  Brenna Flaugher  
    • Affiliation    Fermilab    
    • Title  Dark Energy survey
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