Year: 2009
Type: article
Abstract: We have found for the general class of Modified Gravity Models f ( R , ) 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 , ) and to which the f ( R ) and f ( ) models belong, which however do not have this feature.
Authors: Antonio De Felice, Teruaki Suyama
Institution: UCLouvain
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W3105066767