General Relativity & Quantum Cosmology

The growing catalog of gravitational-wave signals from compact object mergers has allowed us to study the properties of black holes and neutron stars more precisely than ever before and has opened a new window through which to probe the earliest moments in our universe’s history. In this talk, I will demonstrate how current and future gravitational-wave observations can be uniquely leveraged to learn about astrophysics and cosmology. With the current catalog of events detected by the LIGO and Virgo gravitational-wave detectors, I will present evidence for a correlation between the redshift and spin distributions of binary black holes and discuss its astrophysical implications. With joint observations of short gamma-ray bursts and binary neutron star mergers accessible in the next few years, I will describe how to constrain the jet geometry and shed light on the central engine powering these explosions. Finally, with the sensitivities expected for the next generation of gravitational-wave detectors, I will present the statistically optimal method for the simultaneous detection of a foreground of compact binary mergers and a stochastic gravitational-wave background from early-universe processes.

Zoom Link: https://pitp.zoom.us/j/95280675686?pwd=RThMeStWeWl1VlBuV1cvYW8zTXgydz09

Abstract and

Zoom Link: https://pitp.zoom.us/j/91762985902?pwd=djhwYVdsQ25GVVBRVTlwSkQvaDJ4Zz09

In this talk, I will show that supergravity on asymptotically flat spaces possesses a (nonlinear) asymptotic symmetry algebra, containing an infinite number of fermionic generators. Starting from the Hamiltonian action for supergravity with suitable boundary conditions on the graviton and gravitino fields, I will derive a graded extension of the BMS_4 algebra at spatial infinity, denoted by SBMS_4. These boundary conditions are not only invariant under the SBMS_4 algebra, but lead to a fully consistent canonical description of the supersymmetries, which have well-defined Hamiltonian generators. One finds, in particular, that the graded brackets between the fermionic generators yield BMS supertranslations, of which they provide therefore “square roots”.  I will comment on some key aspects of extending the asymptotic analysis at spatial infinity to fermions and on the structure of the SBMS_4 algebra in terms of Lorentz representations.

Zoom link: https://pitp.zoom.us/j/95951230095?pwd=eHIwUXB5SUkvd0IvZnVUN3JJMFE1QT09

The advent of precise measurements of neutron star properties has led to an explosion in "nuclear astrophysics": studying the properties of high-density matter using astrophysical phenomena.  Remarkably, constraints provided by nuclear theory and experiment and high-energy astrophysical observations are now competitive (and often complementary) in constraining the equation of state (EoS) of matter at supernuclear densities.  On the astrophysical side, data have provided a clearer picture how these constraints are affected by the choice of modeling the EoS.  Specifically, the nuclear EoS in astrophysical analyses is usually modeled phenomenologically, and often using ad hoc assumptions.  I will discuss why these ad hoc assumptions will likely cause problems, considering the deluge of coming neutron-star measurements, by comparing these approaches to a data-driven, "nonparametric", model.

Zoom link:  https://pitp.zoom.us/j/94435348102?pwd=OHF2MkNMWStNTlhmdkRQaElNL1M1Zz09