Analyticity of the black hole S-matrix
- 1McGill University
- 2Department of Physics and Astronomy, University of California Los Angeles
Abstract
A bstract : 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.
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BibTeX
@article{correia2026analyticity,
title = {{Analyticity of the black hole S-matrix}},
author = {Miguel Correia and Tushar Gopalka and Giulia Isabella and Anna M. Wolz},
journal = {Journal of High Energy Physics},
year = {2026},
month = oct,
doi = {10.1007/jhep10(2026)150},
url = {https://link.springer.com/article/10.1007/JHEP10(2026)150},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Analyticity of the black hole S-matrix
AU - Miguel Correia
AU - Tushar Gopalka
AU - Giulia Isabella
AU - Anna M. Wolz
PY - 2026
DA - 2026/10/14
JO - Journal of High Energy Physics
DO - 10.1007/jhep10(2026)150
UR - https://link.springer.com/article/10.1007/JHEP10(2026)150
AB - A bstract : 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.
SN - 1029-8479
ER -