A model for the very early Universe

TL;DR

This paper explores a theoretical model of the early universe involving massless fermions with gravitational torsion, showing that certain symmetries break dynamically and predicting a vanishing Hubble parameter in a specific limit.

Contribution

It introduces a novel model with N species of fermions interacting via gravitational torsion, demonstrating symmetry breaking and deriving implications for early universe cosmology.

Findings

Symmetry breaking occurs regardless of the four-fermion coupling value.

The model predicts a zero Hubble parameter when fermions are integrated out.

A Planck-scale axion emerges due to the chiral anomaly.

Abstract

A model with N species of massless fermions interacting via (microscopic) gravitational torsion in de Sitter spacetime is investigated in the limit N->infinity. The U_V(N)*U_A(N) flavor symmetry is broken dynamically irrespective of the (positive) value of the induced four-fermion coupling. This model is equivalent to a theory with free but massive fermions fluctuating about the chiral condensate. When the fermions are integrated out in a way demonstrated long ago by Candelas and Raine, the associated gap equation together with the Friedmann equation predict that the Hubble parameter vanishes. Introducing a matter sector (subject to a finite gauge symmetry) as a source for subsequent cosmology, the neutral Goldstone field acquires mass by the chiral anomaly, resulting in a Planck-scale axion.