• DOI:10.1103/PhysRevD.83.064042
• Corpus ID: 73702522

Anisotropic stress and stability in modified gravity models

@article{Saltas2010AnisotropicSA,
  title={Anisotropic stress and stability in modified gravity models},
  author={Ippocratis D. Saltas and Martin Kunz},
  journal={Physical Review D},
  year={2010},
  volume={83},
  pages={064042}
}

• I. D. Saltas, M. Kunz
• Published 14 December 2010
• Geology
• Physical Review D

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.