Gravitational Wave Propagation in K-essence Cosmology: Theory and Observational Constraints

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Main Authors: Bhunia, Sougata, Guendelman, Eduardo, Gangopadhyay, Debashis, Herrera, Ramón, Bhattacharyya, Abhijit, Manna, Goutam
Format: Preprint
Published: 2026
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author Bhunia, Sougata
Guendelman, Eduardo
Gangopadhyay, Debashis
Herrera, Ramón
Bhattacharyya, Abhijit
Manna, Goutam
author_facet Bhunia, Sougata
Guendelman, Eduardo
Gangopadhyay, Debashis
Herrera, Ramón
Bhattacharyya, Abhijit
Manna, Goutam
contents Gravitational waves (GWs) provide a powerful, theory-independent probe of the dynamical structure of spacetime and the cosmological background. We study linearized GW propagation in k-essence cosmology, where a non-canonical scalar field describes the dark sector. In the high-frequency (short-wavelength) approximation on a Friedmann--Lema\^ıtre--Robertson--Walker (FLRW) background, and restricting to the transverse-traceless tensor sector, we derive a modified evolution equation for tensor perturbations. The GW speed remains strictly luminal, consistent with multimessenger bounds such as GW170817, but the interaction with the background field $\barϕ$ induces a time-dependent effective mass-like term $m_{\rm eff}$. This background-induced mass modifies the dispersion relation without introducing additional propagating degrees of freedom, leading to a cumulative, frequency-dependent phase shift in the waveform over cosmological distances. We show that $m_{\rm eff}$ is uniquely determined by background cosmological parameters and can be written as a redshift-dependent function, $m_{\rm eff}(z)$, directly linking GW observables to scalar-field dynamics, while the GW luminosity distance remains identical to its electromagnetic counterpart, preserving standard-siren consistency. We test the scenario through a joint Bayesian analysis that combines cosmic chronometers (CC), BAO, Pantheon+SH0ES, and standard-siren data from GWTC-2.1/3/4. The reconstruction is consistent with current constraints and reproduces the late-time expansion history, while the evolution of $m_{\rm eff}(z)$ offers a new mechanism that may help alleviate the $H_0$ tension.
format Preprint
id arxiv_https___arxiv_org_abs_2605_25466
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Gravitational Wave Propagation in K-essence Cosmology: Theory and Observational Constraints
Bhunia, Sougata
Guendelman, Eduardo
Gangopadhyay, Debashis
Herrera, Ramón
Bhattacharyya, Abhijit
Manna, Goutam
General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
Gravitational waves (GWs) provide a powerful, theory-independent probe of the dynamical structure of spacetime and the cosmological background. We study linearized GW propagation in k-essence cosmology, where a non-canonical scalar field describes the dark sector. In the high-frequency (short-wavelength) approximation on a Friedmann--Lema\^ıtre--Robertson--Walker (FLRW) background, and restricting to the transverse-traceless tensor sector, we derive a modified evolution equation for tensor perturbations. The GW speed remains strictly luminal, consistent with multimessenger bounds such as GW170817, but the interaction with the background field $\barϕ$ induces a time-dependent effective mass-like term $m_{\rm eff}$. This background-induced mass modifies the dispersion relation without introducing additional propagating degrees of freedom, leading to a cumulative, frequency-dependent phase shift in the waveform over cosmological distances. We show that $m_{\rm eff}$ is uniquely determined by background cosmological parameters and can be written as a redshift-dependent function, $m_{\rm eff}(z)$, directly linking GW observables to scalar-field dynamics, while the GW luminosity distance remains identical to its electromagnetic counterpart, preserving standard-siren consistency. We test the scenario through a joint Bayesian analysis that combines cosmic chronometers (CC), BAO, Pantheon+SH0ES, and standard-siren data from GWTC-2.1/3/4. The reconstruction is consistent with current constraints and reproduces the late-time expansion history, while the evolution of $m_{\rm eff}(z)$ offers a new mechanism that may help alleviate the $H_0$ tension.
title Gravitational Wave Propagation in K-essence Cosmology: Theory and Observational Constraints
topic General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2605.25466