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arXiv · 2111.03338

Big-Bounce in projectively invariant Nieh-Yan models: the Bianchi I case

Flavio Bombacigno·Simon Boudet·Gonzalo J. Olmo·Giovanni Montani
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Abstract

We show that the Nieh-Yan topological invariant breaks projective symmetry and loses its topological character in presence of non vanishing nonmetricity. The notion of the Nieh-Yan topological invariant is then extended to the generic metric-affine case, defining a generalized Nieh-Yan term, which allows to recover topologicity and projective invariance, independently. As a concrete example a class of modified theories of gravity is considered and its dynamical properties are investigated in a cosmological setting. In particular, bouncing cosmological solutions in Bianchi I models are derived. Finite time singularities affecting these solutions are analysed, showing that the geodesic completeness and the regular behavior of scalar perturbations in these space-times are not spoiled.

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Flavio Bombacigno, Simon Boudet, Gonzalo J. Olmo, Giovanni Montani. 2021-11-05. Big-Bounce in projectively invariant Nieh-Yan models: the Bianchi I case. https://arxiv.org/abs/2111.03338

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