Perturbations in massive gravity cosmology

By M. Crisostomi, D. Comelli, L. Pilo. 2012

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A bstractWe study cosmological perturbations for a ghost free massive gravity theory formulated with a dynamical extra metric that is needed to massive deform GR. In this formulation FRW background solutions fall in two branches. In the dynamics of perturbations around the first branch solutions, no extra degree of freedom with respect to GR is present at linearized level, likewise what is found in the Stuckelberg formulation of massive gravity where the extra metric is flat and non dynamical. In the first branch, perturbations are probably strongly coupled. On the contrary, for perturbations around the second branch solutions all expected degrees of freedom propagate. While tensor and vector perturbations of the physical metric that couples with matter follow closely the ones of GR, scalars develop an exponential Jeans-like instability on sub-horizon scales. On the other hand, around a de Sitter background there is no instability. We argue that one could get rid of the instabilities by introducing a mirror dark matter sector minimally coupled to only the second metric.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/42d371f0505a0a49523467a1c4774df23167a9b7

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Citations in the corpus

Testing modified gravity at cosmological distances with LISA standard sirens (2019, methodology): “This information about homogeneous configurations is sufficient for the scope of this work, more details can be found in [139–142].”
Cosmological stability bound in massive gravity and bigravity (2013, background): “20) From now on, we will work in the normal branch for which this relation is true (branch 2 in the language of [25]).”
Massive Gravity (2014, background): “2 Bi-gravity Cosmological solutions in bi-gravity have been considered in [474, 479, 104, 106, 8, 475, 478, 9, 7, 62].”
Cosmological tests of modified gravity (2015, background): “Unfortunately, again these solutions are found to be unstable under linear perturbations [148, 149, 150, 151, 152, 153, 154] unless we tune the Planck scale for the second metric to decouple the massive graviton from matter [155].”
Bimetric gravity is cosmologically viable (2015, background): “Perturbations in the algebraic branch are pathological [29], so we will consider the dynamical branch in which the f -metric lapse is fixed,”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “On the other hand, in the finite branch of solutions one found gradient instabilities (or crossing a singularity) [189, 193, 197] and two ways out have been proposed in the literature”