paper

Analytic solutions for the Bianchi I universe coupled to several barotropic perfect fluids

arXiv:2406.20070 · doi:10.1103/PhysRevD.110.084059

Abstract

We consider the Bianchi I geometry coupled to several species of comoving barotropic perfect fluids with a linear equation of state in the context of general relativity. The solution of the dynamics can be reduced to a quadrature, which can be explicitly performed in certain cases. In particular, we obtain the explicit solution for one species, as well as for two species, given their barotropic indices obey a certain relation. These solutions include and generalize different models studied in the literature. For completeness, we analyze all the different possible signs of the matter energy densities, and we obtain a particularly interesting model in which an exotic species produces a bounce of the scale factor, providing a singularity-free cosmology, and then decays to leave a nonexotic component as the dominant fluid for large volumes.

16 pages. For a better readability, the first version (arXiv:2406.20070v1) has been divided into two independent and self-consistent papers. The present one contains all the results corresponding to the Bianchi I model, while arXiv:2407.17307 contains all the analysis of the Bianchi IX model. Moreover, this new version also includes some plots, and is the version accepted for publication

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