Repulsive gravity in the very early Universe

TL;DR

This paper explores mechanisms that prevent singularities in the early Universe, showing that repulsive effects from spin interactions and gauge symmetry breaking can cause a bounce, avoiding a Big Bang singularity.

Contribution

It introduces two novel classical models where repulsive effects regularize the initial singularity, differing from string cosmology by replacing the dilaton with a radiation fluid.

Findings

Universe undergoes a bounce instead of a singularity

Repulsive spin interactions can halt collapse

Gauge symmetry breaking induces a decelerated expansion

Abstract

I present two examples in which the curvature singularity of a radiation-dominated Universe is regularized by (a) the repulsive effects of spin interactions, and (b) the repulsive effects arising from a breaking of the local gravitational gauge symmetry. In both cases the collapse of an initial, asymptotically flat state is stopped, and the Universe bounces towards a state of decelerated expansion. The emerging picture is typical of the pre-big bang scenario, with the main difference that the string cosmology dilaton is replaced by a classical radiation fluid, and the solutions are not duality-invariant.