DW-genesis: generating the baryon number from domain walls

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.