Scalar-Torsion Mode in a Cosmological Model of the Poincar\'{e} Gauge Theory of Gravity

TL;DR

This paper studies the scalar-torsion mode's equation of state in Poincaré gauge gravity, revealing its evolution across cosmic epochs and its potential to support late-time acceleration, including phantom crossing.

Contribution

It provides a detailed analysis of the scalar-torsion mode's EoS in specific Poincaré gauge gravity models, highlighting its dynamic behavior and cosmological implications.

Findings

Torsion EoS mimics radiation and matter in early universe

Supports late-time cosmic acceleration

Can cross the phantom divide in low redshift regimes

Abstract

We investigate the equation of state (EoS) of the scalar-torsion mode in Poincar\'{e} gauge theory of gravity. We concentrate on two cases with the constant curvature solution and positive kinetic energy, respectively. In the former, we find that the torsion EoS has different values in the various stages of the universe. In particular, it behaves like the radiation (matter) EoS of $w_r=1/3$ ($w_m=0$) in the radiation (matter) dominant epoch, while in the late time the torsion density is supportive for the accelerating universe. In the latter, our numerical analysis shows that in general the EoS has an asymptotic behavior in the high redshift regime, while it could cross the phantom divide line in the low redshift regime.