Catastrogenesis: DM, GWs, and PBHs from ALP string-wall networks

Graciela B. Gelmini, Anna Simpson, Edoardo Vitagliano

Axion-like particles (ALPs), a compelling candidate for dark matter (DM), are the pseudo Nambu-Goldstone bosons of a spontaneously and explicitly broken global $U(1)$ symmetry. Whe…