Bimetric Universe with Matter

We analyze the early stage of evolution of a universe with two scale factors proposed in Falomir et al. [Phys. Rev. D 96, 083534 (2017)PRVDAQ2470-001010.1103/PhysRevD.96.083534]. when matter is present. The scale factors describe two causally disconnected patches of the universe interacting trough a nontrivial Poisson bracket structure in the momentum sector characterized by one parameter κ. We studied two scenarios in which one of the patches is always filled with relativistic matter while the other contains relativistic matter in one case, and nonrelativistic matter in the second case. By solving numerically the set of equations governing the dynamics, we found that the energy content of one sector drains to the other and from here it is possible to constrain the deformation parameter κ by supposing that the decay of the energy density happens, at most, at the Big Bang Nucleosynthesis temperature in order to return to the usual behavior of radiation. The relation with nonstandard cosmologies is also addressed. © 2021 American Physical Society.