Analyticity of the Black Hole S-Matrix

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Hauptverfasser: Correia, Miguel, Gopalka, Tushar, Isabella, Giulia, Wolz, Anna M.
Format: Preprint
Veröffentlicht: 2025
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author Correia, Miguel
Gopalka, Tushar
Isabella, Giulia
Wolz, Anna M.
author_facet Correia, Miguel
Gopalka, Tushar
Isabella, Giulia
Wolz, Anna M.
contents We establish the analytic structure of the S-matrix in the complex-frequency plane for classical wave scattering on a Schwarzschild background in four space-time dimensions. Our argument relies on the analytic continuation of the gravitational potential, with the singularity behind the horizon playing a crucial role. We find that in the lower half-plane the partial-wave amplitudes are analytic except for the quasinormal-mode poles and the branch cut associated with late-time tails. As a direct consequence of causality, the retarded Green's function and absorption amplitude are analytic in the upper-half plane. We show, however, that Stokes phenomena can obstruct this analyticity domain from carrying over to the elastic amplitude, which instead develops a branch-cut in the upper-half plane. We also determine the effect of infrared (IR) regulators on the analytic structure, showing that polynomial boundedness requires a sharp lower bound on the IR cutoff in terms of the Schwarzschild radius.
format Preprint
id arxiv_https___arxiv_org_abs_2511_11794
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Analyticity of the Black Hole S-Matrix
Correia, Miguel
Gopalka, Tushar
Isabella, Giulia
Wolz, Anna M.
High Energy Physics - Theory
General Relativity and Quantum Cosmology
Mathematical Physics
We establish the analytic structure of the S-matrix in the complex-frequency plane for classical wave scattering on a Schwarzschild background in four space-time dimensions. Our argument relies on the analytic continuation of the gravitational potential, with the singularity behind the horizon playing a crucial role. We find that in the lower half-plane the partial-wave amplitudes are analytic except for the quasinormal-mode poles and the branch cut associated with late-time tails. As a direct consequence of causality, the retarded Green's function and absorption amplitude are analytic in the upper-half plane. We show, however, that Stokes phenomena can obstruct this analyticity domain from carrying over to the elastic amplitude, which instead develops a branch-cut in the upper-half plane. We also determine the effect of infrared (IR) regulators on the analytic structure, showing that polynomial boundedness requires a sharp lower bound on the IR cutoff in terms of the Schwarzschild radius.
title Analyticity of the Black Hole S-Matrix
topic High Energy Physics - Theory
General Relativity and Quantum Cosmology
Mathematical Physics
url https://arxiv.org/abs/2511.11794