Asymptotic Cosmological Behavior of Scalar-Torsion Mode in Poincare Gauge Theory

TL;DR

This paper investigates the early universe behavior of scalar-torsion modes in Poincaré gauge gravity, revealing radiation-like asymptotics and stable torsion pressure at high redshift through analytical and numerical methods.

Contribution

It provides new insights into the asymptotic behavior of scalar-torsion modes, including radiation-like evolution and stable pressure, using Laurent expansion and numerical analysis.

Findings

Torsion density behaves as a^{-4} in the early universe.

Torsion pressure approaches one-third of the density at high redshift.

Numerical computations support the analytical results.

Abstract

We study the cosmological effect of the simple scalar-torsion ($0^+$) mode in Poincar\'{e} gauge theory of gravity. We find that for the non-constant (affine) curvature case, the early evolution of the torsion density $\rho_T$ has a radiation-like asymptotic behavior of $a^{-4}$ with $a$ representing the scale factor, along with the stable point of the torsion pressure ($P_T$) and density ratio $P_T/\rho_T\rightarrow 1/3$ in the high redshift regime $(z \gg 0)$, which is different from the previous result in the literature. We use the Laurent expansion to resolve the solution. We also illustrate our result by the execution of numerical computations.