DW-genesis: generating the baryon number from domain walls

TL;DR

This paper proposes a novel mechanism called DW-genesis where axionic domain walls generate the baryon asymmetry through spontaneous baryogenesis, analyzing its efficiency and gravitational wave signals.

Contribution

It introduces DW-genesis as a new baryogenesis mechanism involving axionic domain walls coupled to lepton number, and studies its implications and observational prospects.

Findings

Baryon asymmetry maximized when domain walls collapse at L-violation decoupling

Gravitational wave signals from domain wall annihilation are potentially detectable

Successful DW-genesis often conflicts with observable gravitational wave signals

Abstract

We show that axionic domain walls, when they couple to the lepton number, can generate a net baryon and lepton number through the mechanism of spontaneous baryogenesis. We study systematically the baryon asymmetry produced by these domain walls (DWs) at annihilation, and refer to this process as DW-genesis. We find that the baryon number is maximised when the DW network collapses approximately at the moment when the $L$-violating interaction decouples. We explore the expected gravitational wave signal from the DW network annihilation and the prospects for detecting it, but conclude that successful DW-genesis is typically in tension with observable GW signal. Morever, we briefly discuss a possible suppression induced by the cancellation between the asymmetry created by "opposite" axionic domain walls attached to the string.