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arXiv · 0904.2092

Vacuum structure for scalar cosmological perturbations in Modified Gravity Models

Antonio De Felice·Teruaki Suyama
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Abstract

We have found for the general class of Modified Gravity Models f(R,G) a new instability which can arise in vacuum for the scalar modes of the cosmological perturbations if the background is not de Sitter. In particular, the short-wavelength modes, if stable, in general have a group velocity which depends linearly in k, the wave number. Therefore these modes will be in general superluminal. We have also discussed the condition for which in general these scalar modes will be ghost-like. There is a subclass of these models, defined out of properties of the function f(R,G) and to which the f(R) and f(G) models belong, which however does not have this feature.

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Antonio De Felice, Teruaki Suyama. 2009-06-30. Vacuum structure for scalar cosmological perturbations in Modified Gravity Models. https://doi.org/10.1088/1475-7516/2009/06/034

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