Environmental CPT Violation in an Expanding Universe in String Theory

Understand

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.