Variety of cosmic acceleration models from massive $F(R)$ bigravity

TL;DR

This paper explores various cosmic acceleration models within massive $F(R)$ bigravity, presenting solutions that include Big and Little Rip, quintessence, and de Sitter universes, and analyzing their singularities and metric relations.

Contribution

It introduces new cosmological solutions in massive $F(R)$ bigravity, including cases with coinciding and non-coinciding metrics, and discusses their physical implications.

Findings

Multiple accelerating universe solutions are constructed.

Cosmological singularities in one metric may not appear in the other.

Super-luminal modes are identified in certain solutions.

Abstract

We study the accelerating cosmology in massive $F(R)$ bigravity via the reconstruction scheme. The consistent solution of the FRW equations is presented: it includes Big and Little Rip, quintessence, de Sitter and decelerating universes described by the physical $g$ metric while the corresponding solution of the universe described by the reference $f$ metric is also found. It is demonstrated that in general the cosmological singularities of $g$ metric are not always manifested as cosmological singularities of the reference $f$ metric. We give two consistent ways to describe the Big and Little Rip, quintessence, de Sitter and decelerating universes. In one of the consistent solutions, the two metrics $g$ and $f$ coincide with each other, which may indicate the connection with the convenient single metric background formulation. For another solution, where two metrics $g$ and $f$ do not coincide with each other, here always appears super-luminal mode.