Past Events

  • 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.

  • 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.

  • Condensed Matter Seminar: "Controlling Strong Light Matter Coupling with Photonic Crystals"

    David Rittenhouse Laboratory, A4

    Hui Deng (University of Michigan)

    Microcavity exciton-polaritons provide a unique photonic platform that manifests non-equilibrium quantum orders. It combines strong nonlinearity and rich many-body physics of matter with robust coherence and ready accessibility of light, allowing diverse quantum phenomena at high temperature, on a photonic chip. To go beyond 2D condensation physics, it becomes important to control the fundamental properties of polaritons without destroying the quantum orders.

  • Astro Seminar: "The Milky Way's Dust in Three Dimensions"

    David Rittenhouse Laboratory, A4

    Edward Schlafly (Lawrence Berkeley National Laboratory)

    Most observations of the Milky Way's gas and dust are limited to two dimensions; their angular distribution is precisely measured, but their distribution in distance is much more uncertain.  Large surveys of stars can be used to resolve this uncertainty.  Because light from stars is absorbed and scattered by intervening material before observation on earth, the Galaxy's stars can be used as a dense network of lighthouses to illuminate the structure and properties of the Milky Way's interstellar medium.

  • High Energy Theory Seminar: "Bit Threads in Space and Time"

    David Rittenhouse Laboratory, 2N36

    Matt Headrick (Brandeis University)

    Bit threads are a reformulation of the Ryu-Takayanagi holographic entanglement entropy formula that offer several conceptual advantages over the standard minimal-surface formulation.

  • Condensed Matter Seminar: "Soft matter physics in the gut"

    David Rittenhouse Laboratory, A4

    Sujit S. Datta (Princeton University)

    The gut governs digestion and nutrient absorption, is a promising target for drug delivery, and teems with micro-organisms that can have remarkably strong effects on host health. Despite its importance, however, little is known about how the structure and function of the gut are influenced by many of the soft materials that transit through it regularly.