Dynamical suppression of spacetime torsion

TL;DR

This paper proposes that spacetime torsion was significant in the early universe but diminished over time, explaining its negligible current effects and linking early torsion dynamics to inflation consistent with observational data.

Contribution

It introduces a higher-dimensional braneworld model showing how torsion can dynamically suppress over cosmic evolution, aligning with inflation and observational constraints.

Findings

Torsion was significant in the early universe and decreased over time.

The model predicts inflation with a graceful exit.

Results are consistent with Planck 2018 and BICEP-2 data.

Abstract

A surprising feature of our present four dimensional universe is that its evolution appears to be governed solely by spacetime curvature without any noticeable effect of spacetime torsion. In the present paper, we give a possible explanation of this enigma through ``cosmological evolution'' of spacetime torsion in the backdrop of a higher dimensional braneworld scenario. Our results reveal that the torsion field may had a significant value at early phase of our universe, but gradually decreased with the expansion of the universe. This leads to a negligible footprint of torsion in our present visible universe. We also show that at an early epoch, when the amplitude of the torsion field was not suppressed, our universe underwent through an inflationary stage having a graceful exit within a finite time. To link the model with observational constraints, we also determine the spectral index for curvature perturbation ($n_s$) and tensor to scalar ratio ($r$) in the present context, which match with the results of $Planck$ 2018 (combining with BICEP-2 Keck-Array) data \cite{Planck}.