Past Events

  • Condensed Matter Seminar: "Topological protection of photons"

    David Rittenhouse Laboratory, A4

    Mikael Rechtsman (Penn State University)

    Topological insulators are solid-state materials whose transport properties are immune to defects and disorder due to underlying topological order.  Perhaps the first such phenomenon was the quantum Hall effect, wherein the Hall conductivity is quantized and hence extremely robust.  In this talk, I will present the experimental observation of the topological protection of the transport of photons (rather than electrons in the solid state) in complex dielectric structures.  I will then present the obser

  • HET & HEE Joint Seminar: (TBA)

    Center for Particle Cosmology

    Josh Ruderman (NYU)

  • Rittenhouse Lecture: "GW170817: Hearing and Seeing a Binary Neutron Star Merger"

    David Rittenhouse Laboratory, A8

    Daniel Holz (Enrico Fermi Institute and Kavli Institute for Cosmology, U of Chicago) hosted by Bhuvnesh Jain

    With the discovery of GW170817 in gravitational waves, and the discovery of an associated short gamma-ray burst, and the discovery of an associated optical afterglow, we have finally entered the era of gravitational-wave multi-messenger astronomy. We will discuss LIGO/Virgo's detection of this binary coalescence, and explore some of the scientific implications, including confirmation of the kilonova model and implications for the origin of gold and platinum in the universe, tests of general relativity, and the first standard siren measurement of the Hubble constant.

  • Penn Cafe Event: "Unseen Objects in Our Solar System"

    World Cafe Live 3025 Walnut Street

    Masao Sako (U of Penn)

    Masao Sako will discuss his research on searching for new orbits in the solar system.  He will describe efforts to discover objects beyond the orbit of Neptune, some of which contain valuable information about the complicated dynamical history of the system.  Dr. Sako will also discuss why astronomers think that there is a massive previously-unseen planet out there, called Planet nine, and how it might be found. 

  • High Energy Theory Seminar: “Cosmology of a Fine-Tuned SUSY Higgs”

    David Rittenhouse Laboratory, 2N36

    Matthew Reece (Harvard)

    I will discuss some work in progress that explores whether a mildly fine-tuned Higgs boson, as in (mini-)split supersymmetry, can have interesting or observable cosmological consequences. As moduli fields oscillate, the Higgs can respond and perhaps acquire very large values along a D-flat direction. Possible consequences involve a burst of gravitational wave production and an altered estimate of the number of e-folds of inflation.

  • Condensed Matter Seminar: "Striped Ground States in the Hubbard Model"

    David Rittenhouse Laboratory, A4

    Steven White (University of California, Irvine)

    Solving the 2D Hubbard model is one of the most well-known outstanding problems in theoretical condensed matter physics. Various simulation techniques, such has DMRG and quantum Monte Carlo, have made dramatic strides in recent years, but they have still not provided clearcut answers for the nature of the ground state of the strong-coupling doped model.

  • Dissertation Defense: "Exploring the Universe with the Atacama Cosmology Telescope: Polarization-Sensitive Measurements of the Cosmic Microwave Background"

    David Rittenhouse Laboratory, 3W2

    Marius Lungu (UPenn)

  • High Energy Theory Seminar: "BMS Invariant Fluids"

    David Rittenhouse Laboratory, 2N36

    Robert Penna (Columbia University)

    The Bondi-van der Burg-Metzner-Sachs (BMS) group is the asymptotic symmetry group of asymptotically flat spacetime.  It is related to flat gravity in the same way that the conformal group is related to anti de Sitter gravity.  However, while the conformal group is well known throughout field theory, the BMS group is rather mysterious.  We show that the BMS group is closely related to infinite dimensional symmetry groups governing fluid dynamics.  We use a relationship between gravitating systems and lower dimensional fluids on their boundaries to give a new derivation of

  • High Energy Theory Seminar: "Entanglement at a Scale and Recovery Maps"

    David Rittenhouse Laboratory, 2N36

    Nima Lashkari (MIT)

    I discuss the amount of information in quantum field theory states reduced to a region, that cannot be recovered from its subregion density matrices. One can reconstruct the density matrix from its subregions using recovery maps. The vacuum of a conformal field theory is a quantum Markov state and the fixed point of both transformations. I define the entanglement of scaling as a measure of entanglement at a scale, and mention connections with C-theorems proofs in 2, 3 and 4 dimensions.

  • Astro Seminar:"Probes of Primordial Black Hole Dark Matter"

    David Rittenhouse Laboratory, A4

    Ely Kovetz (Johns Hopkins)

    The LIGO observatory has reported several detections of gravitational waves from the coalescence of binary black holes. We consider the extraordinary possibility that the detected events involving heavier masses are mergers of primordial black holes making up the dark matter in the Universe.