Vacuum structure for scalar cosmological perturbations in Modified Gravity Models
arXiv:0904.2092 · doi:10.1088/1475-7516/2009/06/034
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.
17 pages, 1 figure, uses RevTeX, references added
References in corpus (11)
- Class of viable modified gravities describing inflation and the onset of accelerated expansion
- The Cosmology of Modified Gauss-Bonnet Gravity
- Stability of Cosmological Solution in f(R) Models of Gravity
- Dark energy from modified F(R)-scalar-Gauss-Bonnet gravity
- Causality and the speed of sound
- f(R)-Brane
- Ghost Constraints on Modified Gravity
- Nonlinear growth in modified gravity theories of dark energy
- Attractor scenarios and superluminal signals in k-essence cosmology
- Perturbative aspects and conformal solutions of F(R) gravity
- A Note on the Viability of Gauss-Bonnet Cosmology