Torsion Cosmology and the Accelerating Universe

TL;DR

This paper explores a scalar torsion mode in Poincare gauge gravity, demonstrating through numerical analysis that it can produce oscillating and accelerating expansion behaviors similar to the observed universe.

Contribution

It introduces a scalar torsion mode in cosmology that does not directly interact with matter and can account for cosmic acceleration.

Findings

Scalar torsion can cause oscillating universe expansion.

Suitable parameters yield acceleration similar to observations.

The model does not require matter-torsion interaction.

Abstract

Investigations of the dynamic modes of the Poincare gauge theory of gravity found only two good propagating torsion modes; they are effectively a scalar and a pseudoscalar. Cosmology affords a natural situation where one might see observational effects of these modes. Here we consider only the ``scalar torsion'' mode. This mode has certain distinctive and interesting qualities. In particular this type of torsion does not interact directly with any known matter and it allows a critical non-zero value for the affine scalar curvature. Via numerical evolution of the coupled nonlinear equations we show that this mode can contribute an oscillating aspect to the expansion rate of the Universe. From the examination of specific cases of the parameters and initial conditions we show that for suitable ranges of the parameters the dynamic ``scalar torsion'' model can display features similar to those of the presently observed accelerating universe.