Comments on axions, domain walls, and cosmic strings

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