Université de GenèveDépartement de Physique ThéoriqueCAP Genève

Anisotropic stress and stability in modified gravity models

30. March 2011
Cite as: 
I.D. Saltas, M. Kunz, Phys. Rev. D 83 (2011) 064042 [arXiv:1012.3171]
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The existence of anisotropic stress of a purely geometrical origin seems to be a characteristic of higher order gravity models, and has been suggested as a probe to test these models observationally, for example in weak lensing experiments. In this paper, we seek to find a class of higher order gravity models of f(R,G) type that would give us a zero anisotropic stress and study the consequences for the viability of the actual model. For the special case of a de Sitter background, we identify a subclass of models with the desired property. We also find a direct link between anisotropic stress and the stability of the model as well as the presence of extra degrees of freedom, which seems to be a general feature of higher order gravity models. Particularly, setting the anisotropic stress equal to zero for a de Sitter background leads to a singularity that makes it impossible to reach the de Sitter evolution.


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