Comments on axions, domain walls, and cosmic strings

• Published in: Journal of cosmology and astroparticle physics Vol. 2021; no. 11; pp. 41 - 68
• Main Authors: Dine, Michael, Fernandez, Nicolas, Ghalsasi, Akshay, Patel, Hiren H.
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2021; Institute of Physics (IOP)
• Subjects: ASTRONOMY AND ASTROPHYSICS; axions; Cosmic strings; cosmology connection; Dark matter; dark matter theory; Domain walls; Misalignment; monopoles; particle physics; particle physics - cosmology connection; Questions; Radiation; Strings
• ISSN: 1475-7516; 1475-7516
• DOI: 10.1088/1475-7516/2021/11/041

Axions have for some time been considered a plausible candidate for dark matter. They can be produced through misalignment, but it has been argued that when inflation occurs before a Peccei-Quinn transition, appreciable production can result from cosmic strings. This has been the subject of extensive simulations. But there are reasons to be skeptical about the possible role of axion strings. We review and elaborate on these questions, and argue that parametrically strings are already accounted for by the assumption of random misalignment angles. We review and elaborate on these questions, and provide several qualitative arguments that parametrically strings are already accounted for by the assumption of random misalignment angles. The arguments are base on considerations of the collective modes of the string solutions, on computations of axion radiation in particular models, and reviews of simulations.