Environmental CPT Violation in an Expanding Universe in String Theory

TL;DR

This paper explores how a string theory-based cosmological model with torsion can cause environmental CPT violation, leading to neutrino-antineutrino asymmetries and novel leptogenesis scenarios without requiring CP violation.

Contribution

It introduces a string theory model where background torsion causes CPT violation, affecting fermion dispersion relations and enabling leptogenesis without CP violation.

Findings

Different neutrino and antineutrino densities in equilibrium

Environmental CPT violation induced by string background torsion

Potential new mechanisms for baryogenesis

Abstract

We consider a model of an expanding Universe in string theory that yields `environmental' CPT violation for fermions, in the sense of different dispersion relations for fermions and antifermions. These are induced by a cosmological background with constant torsion provided by the Kalb-Ramond antisymmetric tensor field (axion) of the string gravitational multiplet. This effect induces different densities of neutrinos and antineutrinos while in chemical equilibrium, offering new scenarios for leptogenesis and baryogenesis even in the absence of CP violation.