Institute for Advanced Study/Princeton University Early Universe/Cosmology Lunch Discussion
Topic 1: Tidal deformability from scattering and the role of analytic continuation Topic 2: TBA
Abstract 1: The tidal response of a compact object is a key gravitational-wave observable encoding information about its interior. This link is subtle due to the nonlinearities of general relativity. I will show that considering a scattering process bypasses challenges with potential ambiguities, as the tidal response is determined by the asymptotic in- and outgoing waves at null infinity. As an application of the general method, I will consider scalar waves scattering off a nonspinning black hole and demonstrate that the low-frequency expansion of the tidal response reproduces known results for the Love number and absorption. In addition, I will discuss the definition of the response based on gauge-invariant observables obtained from an effective action description. I will introduce this effective action using Newtonian physics, and furthermore clarify the role of analytic continuation for robustly (i) extracting the response and the physical information it contains, and (ii) distinguishing high-order post-Newtonian corrections from finite-size effects in a binary system. This work is important for interpreting upcoming gravitational-wave data for subatomic physics of ultradense matter in neutron stars, probing black holes and gravity, and looking for beyond-standard-model fields.
Abstract 2: TBA