Gravitational leptogenesis in Natural Inflation

TL;DR

This paper investigates gravitational leptogenesis during natural inflation, finding that the generated lepton asymmetry is insufficient to explain the observed baryon asymmetry, given current CMB constraints.

Contribution

It provides a detailed calculation of leptogenesis from parity-violating gravitational waves in natural inflation, showing its limitations under observational bounds.

Findings

Lepton asymmetry is too small to account for baryon asymmetry

CMB tensor-to-scalar ratio bounds constrain leptogenesis effectiveness

Results are independent of inflaton potential and coupling strength

Abstract

We compute the gravitational leptogenesis generated from the parity-violating gravitational waves sourced by an abelian gauge field coupled to a pseudo-scalar inflation. We show that, once the CMB bound on the tensor-to-scalar ratio is enforced, the lepton asymmetry produced by this mechanism during inflation is too small to account for the observed baryon asymmetry of the universe, irrespectively of the inflaton potential, the strength of its coupling to the gauge field, and the details of reheating.