Hierarchical modeling of gravitational-wave populations for disentangling environmental and modified-gravity effects

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Hauptverfasser: Kejriwal, Shubham, Barausse, Enrico, Chua, Alvin J. K.
Format: Preprint
Veröffentlicht: 2025
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author Kejriwal, Shubham
Barausse, Enrico
Chua, Alvin J. K.
author_facet Kejriwal, Shubham
Barausse, Enrico
Chua, Alvin J. K.
contents The upcoming Laser Interferometer Space Antenna (LISA) will detect up to thousands of extreme-mass-ratio inspirals (EMRIs). These sources will spend $\sim 10^5$ cycles in band, and are therefore sensitive to tiny changes in the general-relativistic dynamics, potentially induced by astrophysical environments or modifications of general relativity (GR). Previous studies have shown that these effects can be highly degenerate for a single source. However, it may be possible to distinguish between them at the population level, because environmental effects should impact only a fraction of the sources, while modifications of GR would affect all. We therefore introduce a population-based hierarchical framework to disentangle the two hypotheses. Using simulated EMRI populations, we perform tests of the null vacuum-GR hypothesis and two alternative beyond-vacuum-GR hypotheses, namely migration torques (environmental effects) and time-varying $G$ (modified gravity). We find that with as few as $\approx 20$ detected sources, our framework can statistically distinguish between these three hypotheses, and even indicate if both environmental and modified gravity effects are simultaneously present in the population. Our framework can be applied to other models of beyond-vacuum-GR effects available in the literature.
format Preprint
id arxiv_https___arxiv_org_abs_2510_17398
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hierarchical modeling of gravitational-wave populations for disentangling environmental and modified-gravity effects
Kejriwal, Shubham
Barausse, Enrico
Chua, Alvin J. K.
General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
The upcoming Laser Interferometer Space Antenna (LISA) will detect up to thousands of extreme-mass-ratio inspirals (EMRIs). These sources will spend $\sim 10^5$ cycles in band, and are therefore sensitive to tiny changes in the general-relativistic dynamics, potentially induced by astrophysical environments or modifications of general relativity (GR). Previous studies have shown that these effects can be highly degenerate for a single source. However, it may be possible to distinguish between them at the population level, because environmental effects should impact only a fraction of the sources, while modifications of GR would affect all. We therefore introduce a population-based hierarchical framework to disentangle the two hypotheses. Using simulated EMRI populations, we perform tests of the null vacuum-GR hypothesis and two alternative beyond-vacuum-GR hypotheses, namely migration torques (environmental effects) and time-varying $G$ (modified gravity). We find that with as few as $\approx 20$ detected sources, our framework can statistically distinguish between these three hypotheses, and even indicate if both environmental and modified gravity effects are simultaneously present in the population. Our framework can be applied to other models of beyond-vacuum-GR effects available in the literature.
title Hierarchical modeling of gravitational-wave populations for disentangling environmental and modified-gravity effects
topic General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2510.17398