Dark-Energy Instabilities induced by Gravitational Waves - Archive ouverte HAL
Article Dans Une Revue Journal of Cosmology and Astroparticle Physics Année : 2020

Dark-Energy Instabilities induced by Gravitational Waves

Résumé

We point out that dark-energy perturbations may become unstable in the presence of a gravitational wave of sufficiently large amplitude. We study this effect for the cubic Horndeski operator (braiding), proportional to αB. The scalar that describes dark-energy fluctuations features ghost and/or gradient instabilities for gravitational-wave amplitudes that are produced by typical binary systems. Taking into account the populations of binary systems, we conclude that the instability is triggered in the whole Universe for |αB |≳ 10−2, i.e. when the modification of gravity is sizeable. The instability is triggered by massive black-hole binaries down to frequencies corresponding to 1010 km: the instability is thus robust, unless new physics enters on even longer wavelengths. The fate of the instability and the subsequent time-evolution of the system depend on the UV completion, so that the theory may end up in a state very different from the original one. The same kind of instability is present in beyond-Horndeski theories for |αH| ≳ 10−20. In conclusion, the only dark-energy theories with sizeable cosmological effects that avoid these problems are k-essence models, with a possible conformal coupling with matter.

Dates et versions

hal-02382016 , version 1 (27-11-2019)

Identifiants

Citer

Paolo Creminelli, Giovanni Tambalo, Filippo Vernizzi, Vicharit Yingcharoenrat. Dark-Energy Instabilities induced by Gravitational Waves. Journal of Cosmology and Astroparticle Physics, 2020, 05, pp.002. ⟨10.1088/1475-7516/2020/05/002⟩. ⟨hal-02382016⟩
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