CPT-Violating Leptogenesis induced by Gravitational Defects

Understand

We explore leptogenesis induced by the propagation of neutrinos in gravitational backgrounds that may occur in string theory.

• The first background is due to linear dilatons and the associated Kalb-Ramond field (axion) in four non-compact space-time dimensions of the string, and can be described within the framework of local effective lagrangians.
• The axion is linear in the time coordinate of the Einstein frame and gives rise to a constant torsion which couples to the fermion spin through a gravitational covariant derivative.
• This leads to different energy-momentum dispersion relations for fermions and anti-fermions and hence leptogenesis.