Past Events

  • Department Colloquium: The Cosmic Barber:"Counting Gravitational Hair in the Solar System and Beyond"

    David Rittenhouse Laboratory, Room A6

    Clifford Will (University of Florida)

    According to general relativity, every self-gravitating object has ``hair'', an array of multipole moments of various types that characterize the body's exterior geometry. In alternative theories of gravity, bodies could also be endowed with more exotic tresses, such as scalar hair. We review how solar system experiments, such as light deflection and time-delay measurements, have placed stringent limits on scalar hair. We describe how experiments such as GRACE have measured with high precision the vast head of Newtonian hair possessed by the Earth.

  • GR Math Seminar: "The graded Lie algebra of general relativity "

    Michael Reiterer (IAS and Penn)

    Several problems can be written as [x,x]=0 where the unknown x
    is an element of degree one in a graded Lie algebra. I show that general
    relativity (the Einstein vacuum equations) can also be put in this form.
    Using this language, I discuss formal perturbation theory; gauge-fixing;
    and some open problems. Familiarity with general relativity is not
    assumed, in fact this talk can be taken to be some kind of introduction
    to general relativity. Based on arxiv.org/abs/1412.5561. Joint work with
    Eugene Trubowitz. 

  • Dissertation Defense: "Single Cells Use Transcriptional Mechanisms to Compensate for Differences in Cell Size and DNA Content"

    David Rittenhouse Laboratory, Room A7

    Olivia Padovan-Merhar (University of Pennsylvania)

  • Dissertation Defense: "Nano-Bio Hybrid Electronic Sensors for Chemical Detection and Disease Diagnostics"

    University of Pennsylvania, Singh Center, Room 035

    Nicholas Kybert, University of Pennsylvania

  • Dissertation Defense:"OPTICAL AND ELECTRONIC INTERACTIONS AT THE NANOSCALE"

    LRSM, Reading Room

    Michael Turk (University of Pennsylvania)

  • Advances in Biomedical Optics Seminar: ""Dual-agent Fluorescence Imaging for Highlighting Receptor-Specific Contrast in Tumors""

    Donner Auditorium, Basement Donner Building- 3400 Spruce St.

    Professor Scott Davis (Dartmouth)

    *Pizza to be served @ 11:45A* 

  • Condensed Matter Seminar: "How challenging is the path from nanoscience to nanotechnology? A computational condensed matter physicist perspective"

    DRL A4

    Vincent Meunier, Rensselaer Polytechnic Institute

    Efforts to assemble functional materials with atomic precision has energized scientists and engineers to eventually lead to the field of nanoscience. The development of nanoscience is a premise for new technological advances with unprecedented functionalities and miniaturization, and scientific scrutiny must now shift to translating nanoscience discoveries into technological realizations.

  • Astro Seminar: "ALMA observations of strongly lensed galaxies: A window into the small-scale structure of dark matter halos"

    David Rittenhouse Laboratory A6

    Yashar Hezaveh (Stanford)

    ALMA is starting to open a new window into the dusty structures of
    the universe. With its milli-arcsec resolution and spectral
    capabilities, among other things, it is promising to teach us
    invaluable lessons about super massive black holes, planet formation,
    dark matter, and the birth of first galaxies.  In this talk, I will
    discuss ALMA observations of strongly lensed galaxies and show how we
    can detect low-mass dark matter subhalos in the lensing galaxies by
    measuring the gravitationally-induced distortions of the lensed

  • Condensed Matter Seminar: "Sloppy Models, Differential Geometry, and How Science Works"

    DRL A4

    James P. Sethna, Cornell University

    Models of systems biology, climate change, ecosystems, and macroeconomics have parameters that are hard or impossible to measure directly. If we fit these unknown parameters, fiddling with them until they agree with past experiments, how much can we trust their predictions? We have found that predictions can be made despite huge uncertainties in the parameters -- many parameter combinations are mostly unimportant to the collective behavior. We will use ideas and methods from differential geometry to explain what sloppiness is and why it happens so often.

  • Astro Seminar: "Halo Bias and its Evolution in the Peak Model"

    David Rittenhouse Laboratory, A6

    Tobias Baldauf (IAS)

    The clustering statistics of galaxies and their host haloes in current and upcoming Large Scale Structure surveys have the potential to put stringent constraints on cosmology and fundamental physics. The understanding of these statistics is complicated by the fact that both the initial conditions and the evolution of halo statistics differ from the underlying matter statistics. We study these complications in the framework of the peak model by first establishing agreement of proto-halo density and momentum statistics in simulations and peak model predictions.