Torsion, Gravity Induced Chiral Symmetry Breaking and Cosmological Bounce

TL;DR

This paper proposes a cosmological bounce model driven by gravitationally induced chiral symmetry breaking, where a condensate causes a bounce without violating symmetries, and explores its implications for early universe dynamics.

Contribution

It extends previous work by explicitly calculating the spinor effective action in curved spacetime and introducing a new interaction term affecting perturbation generation.

Findings

Chiral condensate induces a cosmological bounce without symmetry violation.

Effective action computed up to second order in curvature with derivative corrections.

New interaction term may influence adiabatic perturbations during contraction.

Abstract

In this paper, we elaborate and extend our proposal arXiv:2307.16098 of the cosmological bouncing model in which a chiral condensate violates the null energy condition and induces a bounce. The condensate formation is caused by the gravitational effects that arise in the effective action when the curvature of space-time is non-zero. As the chiral condensation is a vacuum effect, the symmetries of the FRW space-time are not violated. We explicitly calculate the spinor effective action in the presence of a background gravitational field up to second order in curvature and with derivative corrections and also derive the initial conditions of the condensate. In addition, a new interaction term between the condensate and the scalar field is introduced that might be relevant for producing the adiabatic perturbations during the contraction phase. The curvature/energy density stays far from Planckian values throughout this evolution.