Large black-hole scalar charges induced by cosmology in Horndeski theories

Fuente: arXiv
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Autores principales: Babichev, Eugeny, Esposito-Farèse, Gilles, Sawicki, Ignacy, Trombetta, Leonardo G.
Formato: Preprint
Publicado: 2025
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author Babichev, Eugeny
Esposito-Farèse, Gilles
Sawicki, Ignacy
Trombetta, Leonardo G.
author_facet Babichev, Eugeny
Esposito-Farèse, Gilles
Sawicki, Ignacy
Trombetta, Leonardo G.
contents The regularity of black hole solutions, embedded in an expanding Universe, is studied in a subclass of Horndeski theories, namely the sum of the simplest quadratic, cubic and quintic actions. We find that in presence of a time derivative of the scalar field, driven by the cosmological expansion, this regularity generically imposes large scalar charges for black holes, even when assuming strictly no direct coupling of matter to the scalar field. Such charges cause a significant accretion of the scalar field by the black holes, driving its local time derivative to a small value. This phenomenon, together with the Vainshtein screening typical of these theories, strongly suppresses observable scalar effects. We show that this full class of models is consistent with LIGO/Virgo detections of gravitational waves, but that the LISA mission should be able to constrain the coefficient of the quintic term at the $10^{-30}$ level in a self-acceleration scenario, an improvement by 16 orders of magnitude with respect to what is imposed by the speed of gravitational waves.
format Preprint
id arxiv_https___arxiv_org_abs_2504_07882
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Large black-hole scalar charges induced by cosmology in Horndeski theories
Babichev, Eugeny
Esposito-Farèse, Gilles
Sawicki, Ignacy
Trombetta, Leonardo G.
General Relativity and Quantum Cosmology
The regularity of black hole solutions, embedded in an expanding Universe, is studied in a subclass of Horndeski theories, namely the sum of the simplest quadratic, cubic and quintic actions. We find that in presence of a time derivative of the scalar field, driven by the cosmological expansion, this regularity generically imposes large scalar charges for black holes, even when assuming strictly no direct coupling of matter to the scalar field. Such charges cause a significant accretion of the scalar field by the black holes, driving its local time derivative to a small value. This phenomenon, together with the Vainshtein screening typical of these theories, strongly suppresses observable scalar effects. We show that this full class of models is consistent with LIGO/Virgo detections of gravitational waves, but that the LISA mission should be able to constrain the coefficient of the quintic term at the $10^{-30}$ level in a self-acceleration scenario, an improvement by 16 orders of magnitude with respect to what is imposed by the speed of gravitational waves.
title Large black-hole scalar charges induced by cosmology in Horndeski theories
topic General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2504.07882