On the logarithmic Love number of black holes beyond general relativity

Fuente: arXiv
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Main Authors: Garcia-Saenz, Sebastian, Lin, Hongbo
Format: Preprint
Published: 2025
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author Garcia-Saenz, Sebastian
Lin, Hongbo
author_facet Garcia-Saenz, Sebastian
Lin, Hongbo
contents Tidal Love numbers and other response coefficients of black holes sometimes exhibit a logarithmic dependence on scale, or 'running'. We clarify that this coefficient is directly calculable from the structure of the equation obeyed by the field perturbation, and requires no knowledge of the full solution. The derived formula allows us to establish some general results on the existence of logarithmic running. In particular, we show that any static and spherically symmetric spacetime that modifies the Schwarzschild or Reissner-Nordström solutions in a perturbative way must have non-zero logarithmic Love numbers. This applies for instance to all regular black hole metrics. On the other hand, our analysis highlights the importance of the perturbativity assumption: without it, we find explicit black hole solutions beyond general relativity with exactly zero running. We also illustrate the advantage of our method by recovering and extending the known results for the Hayward metric.
format Preprint
id arxiv_https___arxiv_org_abs_2512_19111
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the logarithmic Love number of black holes beyond general relativity
Garcia-Saenz, Sebastian
Lin, Hongbo
General Relativity and Quantum Cosmology
High Energy Physics - Theory
Tidal Love numbers and other response coefficients of black holes sometimes exhibit a logarithmic dependence on scale, or 'running'. We clarify that this coefficient is directly calculable from the structure of the equation obeyed by the field perturbation, and requires no knowledge of the full solution. The derived formula allows us to establish some general results on the existence of logarithmic running. In particular, we show that any static and spherically symmetric spacetime that modifies the Schwarzschild or Reissner-Nordström solutions in a perturbative way must have non-zero logarithmic Love numbers. This applies for instance to all regular black hole metrics. On the other hand, our analysis highlights the importance of the perturbativity assumption: without it, we find explicit black hole solutions beyond general relativity with exactly zero running. We also illustrate the advantage of our method by recovering and extending the known results for the Hayward metric.
title On the logarithmic Love number of black holes beyond general relativity
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2512.19111