Tidal Love Numbers of Neutron Stars in Horndeski Theories

Fuente: arXiv
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Autori principali: Diedrichs, Robin Fynn, Tsujikawa, Shinji, Yagi, Kent
Natura: Preprint
Pubblicazione: 2025
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author Diedrichs, Robin Fynn
Tsujikawa, Shinji
Yagi, Kent
author_facet Diedrichs, Robin Fynn
Tsujikawa, Shinji
Yagi, Kent
contents Precision measurements of the gravitational wave signal from compact binary inspirals allow us to constrain the internal structure of those objects via physical parameters such as the tidal Love numbers. In scalar-tensor theories, one typically finds new types of Love numbers that are usually not considered or simply absent in General Relativity, which further allows us to constrain deviations from General Relativity. Building upon previous results, we present the linear perturbation equations necessary to calculate static and even-parity tidal Love numbers in Horndeski theories, the most general scalar-tensor theories with second-order field equations of motion. We further focus on the quadrupolar Love numbers and demonstrate how these can be extracted from the asymptotic expansion of the perturbation fields. We find that there is a potential ambiguity in extracting the Love numbers in this way, which we resolve by performing supplementary calculations in the effective field theory framework. We show that, in the case of scalar-tensor theories, the tidal Love numbers are not directly given by the $1/r^3$ term in the asymptotic expansion of the perturbation fields, as there is an additional contribution to this term independent of the Love numbers. We calculate such a contribution for a minimally coupled scalar field and also for the Damour-Esposito-Farèse model. For the latter, we find that the Love numbers can differ by $\mathcal{O}(1 \sim 10)\,\%$, if this additional contribution is not taken into account.
format Preprint
id arxiv_https___arxiv_org_abs_2501_07998
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Tidal Love Numbers of Neutron Stars in Horndeski Theories
Diedrichs, Robin Fynn
Tsujikawa, Shinji
Yagi, Kent
General Relativity and Quantum Cosmology
High Energy Physics - Phenomenology
High Energy Physics - Theory
Precision measurements of the gravitational wave signal from compact binary inspirals allow us to constrain the internal structure of those objects via physical parameters such as the tidal Love numbers. In scalar-tensor theories, one typically finds new types of Love numbers that are usually not considered or simply absent in General Relativity, which further allows us to constrain deviations from General Relativity. Building upon previous results, we present the linear perturbation equations necessary to calculate static and even-parity tidal Love numbers in Horndeski theories, the most general scalar-tensor theories with second-order field equations of motion. We further focus on the quadrupolar Love numbers and demonstrate how these can be extracted from the asymptotic expansion of the perturbation fields. We find that there is a potential ambiguity in extracting the Love numbers in this way, which we resolve by performing supplementary calculations in the effective field theory framework. We show that, in the case of scalar-tensor theories, the tidal Love numbers are not directly given by the $1/r^3$ term in the asymptotic expansion of the perturbation fields, as there is an additional contribution to this term independent of the Love numbers. We calculate such a contribution for a minimally coupled scalar field and also for the Damour-Esposito-Farèse model. For the latter, we find that the Love numbers can differ by $\mathcal{O}(1 \sim 10)\,\%$, if this additional contribution is not taken into account.
title Tidal Love Numbers of Neutron Stars in Horndeski Theories
topic General Relativity and Quantum Cosmology
High Energy Physics - Phenomenology
High Energy Physics - Theory
url https://arxiv.org/abs/2501.07998