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arXiv · 2412.10111

Stability of cosmological singularity-free solutions in quadratic gravity

M. Asorey·F. Ezquerro·M. Pardina
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Abstract

We introduce a large family of homogeneous and isotropic cosmological solutions in quadratic gravity which are singularity-free at early and late times. This kind of smooth solutions only emerges beyond the unstable de Sitter branch $3α< β$, $α$ being the coupling of the $R^2$ term and $-β$ the coupling of the $R_{μν}^2$ term. We have analyzed the stability of these singularity-free solutions by computing the second-order variation of the action. The complete analysis shows that a Big Bang can emerge from a singularity-free regime when the parameters of the theory are slightly modified, revealing the unstable nature of this type of solutions.

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M. Asorey, F. Ezquerro, M. Pardina. 2024-12-13. Stability of cosmological singularity-free solutions in quadratic gravity. https://arxiv.org/abs/2412.10111

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