Renormalization in gravitational leptogenesis with pseudo-scalar-tensor coupling

TL;DR

This paper addresses the renormalization of the gravitational Chern-Pontryagin density in pseudo-scalar inflation models, proposing a scheme to remove UV-cutoff dependence and assess the viability of gravitational leptogenesis.

Contribution

It introduces a renormalization method for the Chern-Pontryagin density in gravitational leptogenesis models, clarifying the UV-cutoff dependence issue.

Findings

Renormalized the Chern-Pontryagin density to eliminate UV dependence.

Derived the renormalized lepton number density using minimal subtraction.

Discussed the implications for the viability of gravitational leptogenesis.

Abstract

We consider the renormalization in the pseudo-scalar inflation models with the gravitational Chern-Simons term. In this model, lepton asymmetry is generated from the chiral gravitational waves produced due to the Chern-Simons term through the gravitational chiral anomaly. However, it is known that the naive estimate of the expectation value of the gravitational Chern-Pontryagin density as well as the resultant lepton number density depend on the UV-cutoff scale, which raises a question on their validity. In this paper, we propose a way to renormalize the expectation value of the Chern-Pontryagin density to remove the UV-cutoff dependence. We also discuss the renormalized lepton number density when we adopt the minimal subtraction scheme and the viability of the gravitational leptogenesis scenario.