A Model of Gravitational Leptogenesis

TL;DR

This paper reviews radiatively-induced gravitational leptogenesis (RIGL), a mechanism where quantum effects in curved spacetime generate matter-antimatter asymmetry, and demonstrates its viability in a neutrino see-saw model to explain the universe's baryon asymmetry.

Contribution

It introduces and analyzes RIGL, showing how loop effects in QFT in curved spacetime can produce the observed matter-antimatter asymmetry in the early universe.

Findings

RIGL can generate the observed baryon-to-photon ratio.

Loop effects induce lepton asymmetry in thermal equilibrium.

The mechanism is demonstrated in a see-saw neutrino model.

Abstract

Gravitational leptogenesis is an elegant way of explaining the matter-antimatter asymmetry in the universe. This paper is a review of the recently proposed mechanism of radiatively-induced gravitational leptogenesis (RIGL), in which loop effects in QFT in curved spacetime automatically generate an asymmetry between leptons and antileptons in thermal quasi-equilibrium in the early universe. The mechanism is illustrated in a simple see-saw BSM model of neutrinos, where the lepton-number violating interactions required by the Sakharov conditions are mediated by right-handed neutrinos with Majorana masses of O(10^10) GeV. The Boltzmann equations are extended to include new, loop-induced gravitational effects and solved to describe the evolution of the lepton number asymmetry in the early universe. With natural choices of neutrino parameters, the RIGL mechanism is able to generate the observed baryon-to-photon ratio in the universe today.