Cosmological perturbations in mimetic Horndeski gravity
Frederico Arroja,Nicola Bartolo,Nicola Bartolo,Purnendu Karmakar,Purnendu Karmakar,Sabino Matarrese +5 more
TLDR
In this article, the authors study linear scalar perturbations around a flat FLRW background in mimetic Horndeski gravity and obtain the equation of motion for the comoving curvature perturbation.Abstract:
We study linear scalar perturbations around a flat FLRW background in mimetic Horndeski gravity. In the absence of matter, we show that the Newtonian potential satisfies a second-order differential equation with no spatial derivatives. This implies that the sound speed for scalar perturbations is exactly zero on this background. We also show that in mimetic $G^3$ theories the sound speed is equally zero. We obtain the equation of motion for the comoving curvature perturbation (first order differential equation) and solve it to find that the comoving curvature perturbation is constant on all scales in mimetic Horndeski gravity. We find solutions for the Newtonian potential evolution equation in two simple models. Finally we show that the sound speed is zero on all backgrounds and therefore the system does not have any wave-like scalar degrees of freedom.read more
Citations
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Mimetic gravity: a review of recent developments and applications to cosmology and astrophysics
TL;DR: Mimetic gravity is a Weyl-symmetric extension of General Relativity, related to the latter by a singular disformal transformation, wherein the appearance of a dust-like perfect fluid can mimic cold dark matter at a cosmological level as discussed by the authors.
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Living with ghosts in Horava-Lifshitz gravity
TL;DR: In this article, the authors considered the projectable Horava-Lifshitz model and showed that the decay rate of photons is tiny in a wide range of phenomenologically acceptable parameters.
Journal ArticleDOI
Cosmological dynamics of mimetic gravity
Jibitesh Dutta,Jibitesh Dutta,Wompherdeiki Khyllep,Wompherdeiki Khyllep,Emmanuel N. Saridakis,Emmanuel N. Saridakis,Emmanuel N. Saridakis,Nicola Tamanini,Sunny Vagnozzi,Sunny Vagnozzi +9 more
TL;DR: In this paper, a detailed investigation of the dynamical behavior of mimetic gravity with a general potential for the mimetic scalar field is presented, which can successfully describe the thermal history of the universe, namely the successive sequence of radiation, matter, and dark energy eras.
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Alive and well: mimetic gravity and a higher-order extension in light of GW170817
TL;DR: In this article, a higher-order extension of the original mimetic theory, appearing in the low-energy limit of projectable Hořava-Lifshitz gravity, is considered.
Journal ArticleDOI
Instabilities in Mimetic Matter Perturbations
TL;DR: In this paper, the authors study cosmological perturbations in mimetic matter scenario with a general higher derivative function and calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings.
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