Talks

Scattering amplitudes of massive spin-2 particles generically grow with energy and lead to violations of perturbative unitarity. One way to partially soften such amplitudes is with the infinite towers of particles present in Kaluza-Klein theories. In this talk I will discuss in detail this mechanism of unitarization for general dimensional reductions of pure gravity and show that it leads to some interesting constraints on the eigenfunctions and eigenvalues of the scalar Laplacian on closed manifolds. A consequence of these constraints is that there exists an upper bound on the gaps between Kaluza-Klein excitations of the graviton, which applies also to Calabi-Yau compactifications of string theory.   

Merging compact objects encode a vast deal of information about their progenitor stellar systems, such as the types of galactic environments they were born in, the intricacies of stellar evolution the persisted throughout their lives, and the physics of the supernovae that marked their deaths. In this talk, I will highlight multiple open questions that can be illuminated through a combination of compact objects observations (via gravitational waves and/or electromagnetic radiation) and computational modeling of environments that lead to the formation of black holes and neutron stars. I first focus on how the growing catalog of black hole mergers observed by the LIGO/Virgo network can place constraints on binary black hole formation scenarios, both by uncovering gravitational-wave sources that have features specific to a subset of formation scenarios (such as spins that are anti-aligned from the orbital angular momentum, high masses that occupy the pair instability mass gap, and distinguishable eccentricities at merger) and through pairing Bayesian hierarchical inference with state-of-the-art astrophysical models. Next, I will show how various uncertain aspects of binary stellar evolution and supernova physics can be constrained by phenomena attributed to merging neutron stars, such as enigmatic r-process enrichment in globular clusters and the association between short gamma-ray bursts and their host galaxies.