Past Events

  • Astro Seminar: "What Sets the Maximum Rotation Rate of Neutron Stars? "

    DRL A6

    Ira Wasserman (Cornell)

    The fastest rotating neutron star spins at a frequency of 716 Hz, or a period of about 1.4 milliseconds. This rapidly rotating neutron star was discovered about 30 years after the previous record holder, at 642 Hz.  Almost all equations of state of nuclear matter would permit faster rotation rates. Why don't they exist? 

  • NSF GRFP Fellowship Application Workshops for Graduate Students

    *Once you have signed up for a date, you will receive information on the location and what to do to prepare.*

    Kristen Coakley, Assistant Director Science Outreach Initiative (UPenn)

    If you would like to sign up to attend a workshop, please email Kristen Coakley ( with your preferred date.  All workshops cover the same material so no need to attend more than once.

    Spots are limited and will be assigned on a first come first served basis.  Additional workshops may be scheduled if interest warrants it.

    Other dates are as follows:

  • Math-Bio seminar: "Geography and Adaptation

    Carolyn Lynch Laboratory, RM 318

    Peter Ralph (University of Southern California)

    Most species are distributed across geography, and so can develop regional differences in different parts of the range. These may often be as a result of natural selection, and the geographic scale on which different solutions to evolutionary problems can appear -- the spatial resolution of adaptation -- is determined by a balance between migration, selection, and availability of genetic variation.
  • High Energy Theory Seminar: "TBA"

    DRL 2N36

    Alberto Nicolis (Columbia University)

  • Astro Seminar: "The Local Universe as a Cosmological Lens "

    DRL A6

    Jonathan Hargis (Haverford)

    The local universe serves as a lens through which we can understand the formation of galaxies in a dark energy + cold dark matter(LCDM) context.  Numerical simulations suggest that galaxies grow hierarchically; that is, from the continuous build-up and tidal destruction of dwarf galaxies and globular clusters.  The discovery of numerous satellite dwarf galaxies and tidal stellar streams in the halo of the Milky Way and Andromeda generally support this picture.  However, detailed observations reveal tensions with LCDM and uncertainties in galaxy formation theory on small scale

  • Math-Bio Seminar: "momi: A new method for inferring demography and computing the multipopulation sample frequency spectrum"

    318 Carolyn Lynch Lab

    John A. Kamm, UC Berkeley

    The sample frequency spectrum (SFS) describes the distribution of allele counts at segregating sites, and is a useful statistic for both summarizing genetic data and inferring biological parameters. SFS-based inference proceeds by comparing observed and expected values of the SFS, but computing the expectations is computationally challenging when there are multiple populations related by a complex demographic history.

  • Physics Department Colloquium: "Fluid 'Ratchets' and Biological Locomotion"

    DRL A8

    Jun Zhang (NYU-Courant Institute)

    In this talk, I will discuss a few laboratory experiments that were inspired from examples of biological locomotion. There, solid structures were forced to interact with their surrounding fluid. These structures, or dynamic boundaries, interact with fluid in asymmetric fashions - either because of their anisotropic geometry or by the spontaneous breaking of symmetry in their response to the fluid. When subject to reciprocal forcing, the coupled systems behave in ways that can be described as 'fluid ratchets'.

  • High Energy Theory Seminar: “Thriving From the Vacuum”

    DRL 2N36

    Claudia de Rham (Case University)

    Theories of modified gravity in the infrared usually come hand in hand with additional degrees of freedom which couple to matter at gravitational strength and carry a low strong-coupling scale. By including non-trivial effects from the vacuum I will show how the strong-coupling scale can be raised while keeping the theory fundamentally Lorentz-invariant. This can lead to new features and may alleviate the need for a screening mechanism.

  • Dissertation Defense: "On Abelian and Discrete Symmetries in F-Theory"

    David Rittenhouse Laboratory, 3C6

    Hernan Piragua

  • Condensed Matter Seminar: "The Granular Physics of (Real) Landscapes"

    David Rittenhouse Laboratory, A4

    Doug Jerolmack (University of Pennsylvania)

    The Earth's surface is a granular-fluid interface, shaped by the feedbacks among water/air flow, topography and particle transport. A bewildering array of patterns arise due to the unstable nature of a sheared, granular free-surface; witness dunes, river networks and barrier islands, for example. For almost a century, research on understanding landscape patterns and predicting rates of sediment transport has focused on developing an ever-more detailed description of the turbulent fluid; the coupling to particle motion is often an afterthought.