English

Anisotropic stress and stability in modified gravity models

General Relativity and Quantum Cosmology 2011-05-10 v2 Cosmology and Nongalactic Astrophysics

Abstract

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.

Keywords

Cite

@article{arxiv.1012.3171,
  title  = {Anisotropic stress and stability in modified gravity models},
  author = {Ippocratis D. Saltas and Martin Kunz},
  journal= {arXiv preprint arXiv:1012.3171},
  year   = {2011}
}

Comments

15 pages, v2: Minor changes in the text, typos corrected

R2 v1 2026-06-21T16:58:44.705Z