Gravitational wave luminosity distance in viscous cosmological models
Abstract
We study the socalled Gravitational Wave luminosity distanceredshift relation d _{ L } ^{GW}(z) during cosmological eras driven by nonperfect fluids. In particular, we show that the presence of a shear viscosity in the energy momentum tensor turns out to be the most relevant effect. Within this scenario, a constant shear viscosity imprints the gravitational wave propagation through a friction term δ(z) with a uniquely given redshift dependence. This peculiar evolution predicts a specific shape for the ratio d _{ L } ^{GW}/d _{ L } ^{EM} which tends to a constant value when the sources are at z ≳ 1, whereas scales linearly with the shear viscosity at lower redshifts, regardless of the value of Ω_{ m0}. According to our final discussion, the predicted redshift dependence δ(z) provided by a shear viscosity could be tested by upcoming surveys of multimessenger sources against analogous scenarios provided by some widely studied theories of modified gravity.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 August 2022
 DOI:
 10.1088/14757516/2022/08/064
 arXiv:
 arXiv:2203.13368
 Bibcode:
 2022JCAP...08..064F
 Keywords:

 gravitational waves / theory;
 Gravitational waves in GR and beyond: theory;
 Cosmological perturbation theory in GR and beyond;
 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Theory
 EPrint:
 19 pages, 4 figures. References and clarifications added. Conclusions unchanged. Accepted for publication in JCAP