Past Events

Penn Cafe Event: "Unseen Objects in Our Solar System"
December 5, 2017  6:00 pm  7:00 pm
World Cafe Live 3025 Walnut Street
Masao Sako (U of Penn)
Masao Sako will discuss his research on searching for new orbits in the solar system. He will describe efforts to discover objects beyond the orbit of Neptune, some of which contain valuable information about the complicated dynamical history of the system. Dr. Sako will also discuss why astronomers think that there is a massive previouslyunseen planet out there, called Planet nine, and how it might be found.

High Energy Theory Seminar: “Cosmology of a FineTuned SUSY Higgs”
December 4, 2017  2:00 pm
David Rittenhouse Laboratory, 2N36
Matthew Reece (Harvard)
I will discuss some work in progress that explores whether a mildly finetuned Higgs boson, as in (mini)split supersymmetry, can have interesting or observable cosmological consequences. As moduli fields oscillate, the Higgs can respond and perhaps acquire very large values along a Dflat direction. Possible consequences involve a burst of gravitational wave production and an altered estimate of the number of efolds of inflation.

Condensed Matter Seminar: "Striped Ground States in the Hubbard Model"
November 29, 2017  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Steven White (University of California, Irvine)
Solving the 2D Hubbard model is one of the most wellknown outstanding problems in theoretical condensed matter physics. Various simulation techniques, such has DMRG and quantum Monte Carlo, have made dramatic strides in recent years, but they have still not provided clearcut answers for the nature of the ground state of the strongcoupling doped model.

Dissertation Defense: "Exploring the Universe with the Atacama Cosmology Telescope: PolarizationSensitive Measurements of the Cosmic Microwave Background"
November 27, 2017  3:00 pm
David Rittenhouse Laboratory, 3W2
Marius Lungu (UPenn)

High Energy Theory Seminar: "BMS Invariant Fluids"
November 27, 2017  2:00 pm
David Rittenhouse Laboratory, 2N36
Robert Penna (Columbia University)
The Bondivan der BurgMetznerSachs (BMS) group is the asymptotic symmetry group of asymptotically flat spacetime. It is related to flat gravity in the same way that the conformal group is related to anti de Sitter gravity. However, while the conformal group is well known throughout field theory, the BMS group is rather mysterious. We show that the BMS group is closely related to infinite dimensional symmetry groups governing fluid dynamics. We use a relationship between gravitating systems and lower dimensional fluids on their boundaries to give a new derivation of

High Energy Theory Seminar: "Entanglement at a Scale and Recovery Maps"
November 20, 2017  2:00 pm
David Rittenhouse Laboratory, 2N36
Nima Lashkari (MIT)
I discuss the amount of information in quantum field theory states reduced to a region, that cannot be recovered from its subregion density matrices. One can reconstruct the density matrix from its subregions using recovery maps. The vacuum of a conformal field theory is a quantum Markov state and the fixed point of both transformations. I define the entanglement of scaling as a measure of entanglement at a scale, and mention connections with Ctheorems proofs in 2, 3 and 4 dimensions.

Astro Seminar:"Probes of Primordial Black Hole Dark Matter"
November 15, 2017  2:00 pm
David Rittenhouse Laboratory, A4
Ely Kovetz (Johns Hopkins)
The LIGO observatory has reported several detections of gravitational waves from the coalescence of binary black holes. We consider the extraordinary possibility that the detected events involving heavier masses are mergers of primordial black holes making up the dark matter in the Universe.

Condensed Matter Seminar: "Tuning Quantum Materials with Uniaxial Strain"
November 15, 2017  4:00 am  5:00 pm
David Rittenhouse Laboratory, A4
Abhay Narayan Pasupathy (Columbia University)
What is the effect of stretching a crystal along a given direction by a small amount? In general, one might not expect much: a change in lattice constant, accompanied by corresponding changes in the electronic and vibrational properties of a crystal. I will describe a few cases of materials where the effect of stretching (ie, uniaxial strain) lead to large and unexpected effects.

HET & HEE Joint Seminar: "Composite Higgses"
November 14, 2017  1:30 pm
Center for Particle Cosmology
Csaba Csaki (Cornell University)

High Energy Theory Seminar: "What Can Cosmology Tell Us About Gravity?"
November 13, 2017  2:00 pm
David Rittenhouse Laboratory, 2N36
Levon Pogosian (Simon Fraser University)
I will review the current status and future prospects of testing theories of gravity using data from largescale structure surveys. I will then discuss certain aspects of the socalled modelindependent tests of dark energy and modified gravity. One is the choice of priors when trying to constrain unknown functions of redshift. Another is the physical interpretation of such tests and their implications for particular types of modified gravity theories.