Leptogenesis via Axion Oscillations after Inflation

TL;DR

This paper proposes a novel leptogenesis mechanism driven by axion oscillations after inflation, which generates baryon asymmetry through lepton number violation mediated by heavy Majorana neutrinos, independent of their CP phases.

Contribution

It introduces a minimal, non-thermal leptogenesis model utilizing axion-induced chemical potentials, effective even with heavy neutrino masses near the GUT scale.

Findings

Successful baryogenesis achieved with heavy neutrino masses near GUT scale.

Reheating temperature must be at least 10^12 GeV for the mechanism to work.

Insensitivity to CP-violating phases in the heavy neutrino sector.

Abstract

Once a light axionlike scalar field couples to the electroweak gauge bosons, its classical motion during reheating induces an effective chemical potential for the fermion number. In the presence of rapid lepton number (L)-violating processes in the plasma, such a chemical potential provides a favorable opportunity for baryogenesis via leptogenesis. We are able to demonstrate that L violation due to the exchange of heavy Majorana neutrinos is sufficient for a successful realization of this idea. Our mechanism represents a novel and minimal alternative to thermal leptogenesis, which turns out to be insensitive to the masses and CP-violating phases in the heavy neutrino sector. It is consistent with heavy neutrino masses close to the scale of grand unification and, quite complementary to thermal leptogenesis, requires the reheating temperature to be at least of order 10^12 GeV.