2018/08/31 by C. P. Burgess, Ryan Plestid, Markus Rummel · 38 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Black Holes and Theoretical Physics #Black hole (networking) #Boundary (topology) #Boundary value problem #Effective field theory #General relativity #Observable #Pulsars and Gravitational Waves Research #Quasinormal mode #Regularization (linguistics) #Schwarzschild radius #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1007/jhep09(2018)113
published in Journal of High Energy Physics 2018(9) (Springer Nature) · v3: clarified role of IR Black Hole fixed point w.r.t. parameter ξ. v2: now published in JHEP; references added, changed definition of time delay and phase in echo spacing
openalex created_date 2018/08/22 · openalex publication_date 2018/09/01 · arxiv created 2020/05/31 · arxiv updated 2020/06/02 · openalex updated_date 2026/08/05
A bstract Gravitational wave ‘echoes’ during black-hole merging events have been advocated as possible signals of modifications to gravity in the strong-field (but semiclassical) regime. In these proposals the observable effect comes entirely from the appearance of nonzero reflection probability at the horizon, which vanishes for a standard black hole. We show how to apply EFT reasoning to these arguments, using and extending earlier work for localized systems that relates choices of boundary condition to the action for the physics responsible for these boundary conditions. EFT reasoning applied to this action argues that linear ‘Robin’ boundary conditions dominate at low energies, and we determine the relationship between the corresponding effective coupling (whose value is the one relevant low-energy prediction of particular modifications to General Relativity for these systems) and the phenomenologically measurable near-horizon reflection coefficient. Because this connection involves only near-horizon physics it is comparatively simple to establish, and we do so for perturbations in both the Schwarzschild geometry (which is the one most often studied theoretically) and the Kerr geometry (which is the one of observational interest for post-merger ring down). In passing we identify the renormalization-group evolution of the effective couplings as a function of a regularization distance from the horizon, that enforces how physics does not depend on the precise position where the boundary conditions are imposed. We show that the perfect-absorber/perfect-emitter boundary conditions of General Relativity correspond to the only fixed points of this evolution. Nontrivial running of all other RG evolution reflects how modifications to gravity necessarily introduce new physics near the horizon.