Majorana propagator on de Sitter space

TL;DR

This paper constructs the Majorana fermion propagator in de Sitter space, finds it identical to the Dirac propagator, and explores implications for one-loop effective actions and flavor mixing.

Contribution

It provides the first explicit construction of Majorana propagators in de Sitter space and compares their quantum effects to Dirac fermions.

Findings

Majorana propagator identical to Dirac propagator in de Sitter space

One-loop effective action for Majorana fermions is half that of Dirac fermions

Derived propagators for flavor mixing relevant to CP violation studies

Abstract

We study the dynamics of Majorana fermions in an expanding de Sitter space and to that aim we construct the vacuum Feynman propagator for Majorana fermions in de Sitter space. Surprisingly, the Majorana propagator is identical to that of the Dirac fermions. We then use this propagator and calculate the one-loop effective action for Majorana fermions, and show that it differs from that of Dirac fermions by a factor of 1/2, which accounts for the reduced number of degrees of freedom of the Majorana particle. Finally, we derive the Majorana and Dirac propagators for mixing fermionic flavors, which are suitable for studying CP-violating effects in quantum loops.