Past Events

**CANCELLED** Astro Seminar: (TBA)
January 31, 2018  2:00 pm
David Rittenhouse Laboratory, A4
TBA

High Energy Theory Seminar: "Naturally Stabilizing the Weak Scale without Partners"
January 29, 2018  2:00 pm
David Rittenhouse Laboratory, 2N36
Devin Walker (Dartmouth College)
We generalize and adapt Veltman's condition to create a framework which naturally addresses the little hierarchy problem. The resulting class of models is economical and ensures a minimum amount of finetuning for the bare Standard Model Higgs mass. To demonstrate this framework, we provide a model with an extended Higgs sector and a top Yukawa coupling that is no longer unity. The latter alleviates the largest radiative corrections to the Higgs mass. The former features significant dimensionfull coupl

Condensed Matter Seminar: "Mechanical Cell Biology of Microbes"
January 24, 2018  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Enrique Rojas (Stanford University)
Research in microbial physiology has traditionally focused on understanding biochemical pathways and, more recently, on elucidating the surprisingly complex structure of microbial cytoplasm. On the other hand, the whether mechanical forces also play a role in controlling subcellular processes in microbes has been overlooked. I will highlight several novel paradigms by which microbes use mechanical (and electrical) factors as signals to control cell growth, division, and survival, and highlight how the remarkable mechanical properties of the cells are critical for these p

**CANCELLED** Astro Seminar: "The Twisted Universe: The Cosmic Quest to Reveal Which End is Up"
January 24, 2018  2:00 pm
David Rittenhouse Laboratory, A4
Brian Keating (UCSD)
The cosmic microwave background (CMB) has spectacularly advanced our understanding of the origin, composition, and evolution of our universe. Yet there is still much to glean from this, the oldest light in the universe. Powerful telescopes are plying the skies in a quest to discover new physics. This talk concentrates on measurements by cuttingedge CMB telescopes which offer a glimpse into an exhilarating, and largely unexplored branch of astrophysics: the search for unique signatures in the polarization of the CMB.

Condensed Matter Seminar: "Topological protection of photons"
January 10, 2018  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Mikael Rechtsman (Penn State University)
Topological insulators are solidstate materials whose transport properties are immune to defects and disorder due to underlying topological order. Perhaps the first such phenomenon was the quantum Hall effect, wherein the Hall conductivity is quantized and hence extremely robust. In this talk, I will present the experimental observation of the topological protection of the transport of photons (rather than electrons in the solid state) in complex dielectric structures. I will then present the obser

HET & HEE Joint Seminar: (TBA)
December 12, 2017  1:30 pm
Center for Particle Cosmology
Josh Ruderman (NYU)

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.

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.