Cosmology in Poincare gauge gravity with a pseudoscalar torsion

TL;DR

This paper develops a cosmological model within Poincare gauge gravity featuring pseudoscalar torsion, where the cosmological constant emerges naturally from geometry, addressing dark energy and related problems without artificial assumptions.

Contribution

It introduces a novel cosmological framework in Poincare gauge gravity with pseudoscalar torsion, deriving the cosmological constant from geometric properties and providing analytic solutions.

Findings

The cosmological constant is intrinsic to the vacuum geometry.

The model's evolution of dark energy matches observational data.

Analytic solutions are obtained and compared with LCDM.

Abstract

A cosmology of Poincare gauge theory is developed, where several properties of universe corresponding to the cosmological equations with the pseudoscalar torsion function are investigated. The cosmological constant is found to be the intrinsic torsion and curvature of the vacuum universe and is derived from the theory naturally rather than added artificially, i.e. the dark energy originates from geometry and includes the cosmological constant but differs from it. The cosmological constant puzzle, the coincidence and fine tuning problem are relieved naturally at the same time. By solving the cosmological equations, the analytic cosmological solution is obtained and can be compared with the LCDM model. In addition, the expressions of density parameters of the matter and the geometric dark energy are derived, and it is shown that the evolution of state equations for the geometric dark energy agrees with the current observational data. At last, the full equations of linear cosmological perturbations and the solutions are obtained.