Past Events

  • High Energy Theory seminar: "Conformally Soft Photons and Gravitons"

    David Rittenhouse Laboratory, 2N36

    Laura Donnay, Harvard University

    In this talk, the four-dimensional S-matrix is reconsidered as a correlator on the celestial sphere at null infinity. Asymptotic particle states can be characterized by the point at which they enter or exit the celestial sphere as well as their SL(2,C) Lorentz quantum numbers: namely their conformal scaling dimension and spin instead of the energy and momentum. This characterization precludes the notion of a soft particle whose energy is taken to zero. I will propose it should be replaced by the notion of a "conformally soft" particle with h=0 or \bar h=0.

  • Women in Physics Public Lecture: "The Most Magnificent Map Ever Made"

    Ben Franklin Room, Houston Hall

    Beth Willman, University of Arizona

    For all of history, humans have observed the Milky Way galaxy by eye as a structure encircling our night sky. However, only within the last 100 years have humans learned that the Milky Way is not the only galaxy in the Universe. Within the last two decades, we have learned that the Sun is one of hundreds of billions of stars in the Milky Way, that the Milky Way is one of hundreds of billions of galaxies in the Universe, and that galaxies exist that are only one ten millionth as luminous as the Milky Way.

  • Advances in Biomedical Optics seminar: “Traumatic microvascular injury: A potentially treatable endophenotype of TBI"

    Donner Auditorium, Basement, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA

    Ramon Diaz-Arrastia, University of Pennsylvania

    Pizza will be served at 11:45 am.

  • Special Condensed Matter seminar: "Anomalous charge and thermal transport in antiferromagnetic Weyl semimetals"

    David Rittenhouse Laboratory, 2N36

    Binghai Yan, Weizmann Institute of Science, Israel

    Topological Weyl semimetals provide a new stage to examine exotic transport phenomena such as the chiral anomaly and the anomalous Hall effect. In the ordinary longitudinal transport, the Wiedemann-Franz law links the ratio of electronic charge and heat conductivity to fundamental constants. It has been tested in numerous solids, but the extent of its relevance to the anomalous transverse transport, which represents the topological nature of the wave function, remains an open question. In this talk, I will first introduce recently-discovered Weyl materials Mn3Sn and Mn3Ge.

  • Joint High Energy Experiment/Theory seminar

    David Rittenhouse Laboratory, 2N36

    Zack Lasner, Yale University

  • Condensed Matter seminar: "Delving Into the Nanoscale World With Thin-Film Nanofluidic Devices"

    David Rittenhouse Laboratory, A4

    Jason R. Dwyer, University of Rhode Island

    Thin film nanofluidic devices offer a diverse range of platform architectures and capabilities for nanoscale sample characterization and single-molecule sensing.

  • Astronomy seminar: "The Hercules Stream: stars on Trojan orbits visiting the solar vicinity"

    David Rittenhouse Laboratory, A2

    Elena D’Onghia (University of Wisconsin-Madison)

    The origin of the stars with coherent velocities discovered in the solar neighborhood remains uncertain, but their dynamics and evolution are key to understanding the dynamics of the Galactic stellar disk and ultimately the history of the Milky Way. The Gaia satellite is currently mapping the phase-space of a few million stars in the solar neighborhood. About 350,000 stars within 200 pc of the Sun are identified in streams, bundles of stars that move together in the same direction with a velocity that is distinct from neighboring stars.

  • Special Seminar: "This Is Not A Diversity Talk"

    David Rittenhouse Laboratory, A8

    John Asher Johnson, Harvard University

    The American discourse on the various disparities present in society generally, and academia specifically, focuses primarily on observations of the state of a given situation---e.g. a lack of diversity---rather than on the actions that lead to such a state. This approach is just as dissatisfying and ultimately ineffectual as observing that certain stars are "bright," rather than describing any of the physical principles that lead to the observed properties of a star.

  • High Energy Theory seminar: "Direct Detection of sub-GeV Dark Matter: A New Frontier"

    David Rittenhouse Laboratory, A8

    Rouven Essig, Stony Brook University

    Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity.  While most experimental searches focus on Weakly Interacting Massive Particles (WIMPs) with masses above the proton (about 1 GeV/c^2), it is important to also consider other motivated dark-matter candidates.  Indeed, over the last decade, the theoretical landscape of possible dark-matter candidates has expanded significantly to consider masses from 10^-22 eV/c^2 up to the Planck mass, and even higher in the case of composite dark matter.  At the same time, many novel dark-ma

  • Condensed Matter seminar: "Fracton phase of matter: Lattice models, gauge theories and realizations"

    David Rittenhouse Laboratory, A4

    Yizhi You, Princeton University

    Fracton phase of matter shares many features of topological order, including long-range entangled ground states and non-trivial braiding statistics. At the same time, fracton phase contains subextensive ground-state degeneracy and the restricted mobility of quasiparticle which exclude itself from the TQFT paradigm. In this talk, I start from several solvable lattice models as candidates for Fracton order. Further, I will present a theoretical framework on higher rank Chern-Simons theory in 3D as the low energy effective theory for Fracton phase.