期刊
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
卷 -, 期 6, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2009/06/034
关键词
modified gravity; cosmological perturbation theory; dark energy theory
资金
- Belgian Federal Office for Scientific
- Technical and Cultural Affairs through the Interuniversity Attraction Pole P6/11
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 do not have this feature.
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