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      A general theory of linear cosmological perturbations: stability conditions, the quasistatic limit and dynamics

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          Abstract

          We analyse cosmological perturbations around a homogeneous and isotropic background for scalar-tensor, vector-tensor and bimetric theories of gravity. Building on previous results, we propose a unified view of the effective parameters of all these theories. Based on this structure, we explore the viable space of parameters for each family of models by imposing the absence of ghosts and gradient instabilities. We then focus on the quasistatic regime and confirm that all these theories can be approximated by the phenomenological two-parameter model described by an effective Newton's constant and the gravitational slip. Within the quasistatic regime we pinpoint signatures which can distinguish between the broad classes of models (scalar-tensor, vector-tensor or bimetric). Finally, we present the equations of motion for our unified approach in such a way that they can be implemented in Einstein-Boltzmann solvers.

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          Second-order scalar-tensor field equations in a four-dimensional space

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            Author and article information

            Journal
            27 November 2017
            Article
            1711.09893

            http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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            gr-qc hep-th

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