Past Events

  • HET & HEE Joint Seminar: "Unification from Scattering Amplitudes"

    David Rittenhouse Laboratory, 4N12

    Cliff Cheung (Caltech)

    Scattering amplitudes are fundamental observables that encode the dynamics of interacting particles. In this talk, I describe how to systematically construct these objects without reference to a Lagrangian or an underlying spacetime. The physics of real-world particles like gravitons, gluons, and pions are thus derived from the properties of amplitudes rather than vice versa. Remarkably, the expressions gleaned from this line of attack are marvelously simple, revealing new structures long hidden in plain sight.

  • High Energy Theory Seminar: "Coarse-Graining Holographic Entanglement"

    David Rittenhouse Laboratory, 2N36

    Netta Engelhardt (Princeton)

  • Astro Seminar: "Cosmic Microwave Backlight: Illuminating Large-Scale Structure with the Universe's Oldest Photons"

    David Rittenhouse Laboratory, A2

    Colin Hill (IAS/Flatiron Institute)

    Studies of the cosmic microwave background (CMB) radiation have driven the current era of precision cosmology.  The tightest cosmological constraints to date have been derived from the primary CMB anisotropies, which predominantly probe the universe in its infancy.  However, CMB experiments have recently entered a new regime in which constraints derived from the secondary anisotropies -- sourced by effects between our vantage point and the surface of last scattering -- substantially improve upon those derived from the primary anisotropies alone.

  • Condensed Matter Seminar: "Structure and Topology of Band Structures in the 1651 Magnetic Space Groups"

    David Rittenhouse Laboratory, A4

    Ashvin Vishwanath (Harvard University)

    We describe a powerful theoretical approach to studying electronic band structures, which associates them with elements of a vector space. The set of consistent band structures in a space group can then be expanded in terms of a small set of basis vectors. We calculate the dimension of this vector space, and the necessary electron fillings to obtain band insulators in all magnetic space groups.

  • Astro Seminar: "Moving Mesh Astrophysics"

    David Rittenhouse Laboratory, A4

    Paul Duffel (UC Berkeley)

    Novel methods in recent years have been developed for numerically solving the hydrodynamical and MHD equations relevant to all kinds of astrophysical flows.  I will first (briefly) present one such computational technique, where the numerical grid follows the MHD flow using a "moving mesh".  I will then present some astrophysical scenarios for which I have applied this method, including planet formation and high-energy transients such as supernovae and gamma ray bursts.

  • High Energy Theory Seminar: "Some New Mechanisms for Baryogenesis"

    David Rittenhouse Laboratory, 2N36

    Jeremy Sakstein (U of Penn)

    There is more matter than antimatter in the universe, and the origin of this asymmetry is still a mystery. The asymmetry can be generated dynamically in the early universe in a process referred to as baryogenesis but the standard model is not able to produce the amount observed. This is one hint that there is physics beyond the standard model. In this talk, I will present two new baryogenesis mechanisms, one using scalar-tensor theories and the other using Lorentz violating theories.

  • Condensed Matter Seminar: "Enhanced optical and magnetic microscopy by orientation-dependent modulation of single-molecule and nitrogen-vacancy-center emission"

    David Rittenhouse Laboratory, A4

    Mikael Backlund (Harvard University)

    Selection rules impose geometrical constraints on the interactions of light and matter. In
    particular, an emitter with a well-defined orientation will emit photons of a characteristic
    polarization and wavevector distribution, even as viewed in the far field. Knowledge of these
    distributions can be leveraged to enhance a number of state-of-the-art microscopy techniques. In
    the first part of the talk I will discuss such an approach to single-molecule localization
    microscopy, relevant for single-molecule tracking and super-resolution imaging. It is known that

  • Astro Seminar:"Probing Galaxy Formation with Modern Cosmological Simulations"

    David Rittenhouse Laboratory, A4

    Paul Torrey (MIT)

    Cosmological simulations are among the most powerful tools available to probe the non-linear regime of cosmic structure formation.  They also provide a clear test-bed for understanding the impact that hydrodynamics and feedback processes have on the evolution of galaxies.  I will present an overview of modern galaxy formation simulations that couple a novel moving mesh computational method with explicit baryon feedback prescriptions.

  • Astro Seminar: "Turbulent Beginnings: A Predictive Theory of Star Formation in the Interstellar Medium"

    David Rittenhouse Laboratory, A2

    Blakesley Burkhart (CfA)

    Our current view of the interstellar medium (ISM) is as a multiphase environment where magnetohydrodynamic (MHD) turbulence affects many key processes. These include star formation, cosmic ray acceleration, and the evolution of structure in the diffuse ISM.  In this talk, I shall review the fundamentals of galactic turbulence and then discuss progress in the development of new techniques for comparing observational data with numerical MHD turbulence simulations.

  • Department Colloquium: "Discovering the Highest Energy Neutrinos Using a Radio Phased Array"

    David Rittenhouse Laboratory, A8

    Abigail Vieregg (University of Chicago) hosted by: Mark Devlin

    Ultra-high energy neutrino astronomy sits at the boundary between particle physics and astrophysics. The detection of high energy neutrinos is an important step toward understanding the most energetic cosmic accelerators and would enable tests of fundamental physics at energy scales that cannot easily be achieved on Earth.