Talks

The sequencing of ancient genomes has provided an unprecedented opportunity to study human evolutionary history over thousands of years, in different regions of the world. Here, I will describe several methods developed in our group to relate genomic data to informative parameters about population expansions, movement and adaptation, while explicitly accounting for both spatial and temporal dimensions. These include a new way to model the spread of ancestry in ancient genomes across a landscape, along with a new simulation framework for easily generating spatial simulations of arbitrary complexity. We have recently applied some of these methods to a new dataset including thousands of ancient human genomes and used them to infer major population movements over the past 13 millennia of Eurasian history.

We present a new class of supersymmetric localization principles in the context of supersymmetric quantum mechanics. Contrary to the standard localization, this new principle deals with non-supersymmetric observables. We apply this to provide a path integral understanding of trace formulas in mathematics. Our examples will contain both integrable and chaotic quantum systems, namely trace formulas on compact Lie groups by Eskin, and generic locally symmetric space by Selberg. 

Zoom Link:  https://pitp.zoom.us/j/99332291865?pwd=c0kyUUlWN1AxeXpvNmRkNHRSRXNXdz09

I will argue that many theories in which dark matter is light (with a mass < eV) lead to theoretically and observationally interesting dark matter substructure. As a particular, calculable, example I will show that this is the case for a new vector boson with non-zero mass (a `dark photon') that is present during inflation, at which time a relic abundance is automatically produced from vacuum fluctuations.  Due to a remarkable coincidence between the size of the primordial density perturbations and the scale at which quantum pressure is relevant, a substantial fraction of the dark matter inevitably collapses into gravitationally bound solitons, which are fully quantum coherent objects. The central densities of these `dark photon star', or `Proca star', solitons are typically a factor 10^6 larger than the local background dark matter density today. I will also mention how similar substructure might occur in theories of post-inflationary axion-like-particles. 

Zoom Link:  https://pitp.zoom.us/j/94995778057?pwd=T2w4WWU0ZGtwWEIzTHFSZ3J6dGovUT09