Speaker: Andrew Spiers (University of Nottingham)
Title: Fix the frame, resolve the memory: The Bondi--Sachs gauge in black hole perturbation theory
Abstract: Understanding gauge and frame dependence is crucial for comparing binary models and extracting physical observables. Black hole perturbation theory calculations are extending to second-order, where increased gauge dependence brings new challenges: gauge-invariant quantities at linear order become gauge-dependent at second-order, and nonlinear source terms can produce infrared divergences. Additionally, gravitational wave memory, a frame-dependent effect, appears at second order and will be detectable with next-generation detectors. In this seminar, I review second-order black hole perturbation theory, the Bondi--Sachs gauge, the BMS frame, and memory effects; by combining these elements, I construct a gauge invariant second-order field equation associated with an asymptotically flat gauge with the appropriate frame to extract the memory.
Room: Sala de Reuniões e Seminários (2-8.3, 2nd Floor of Physics Building)