Comments on Axions, Domain Walls, and Cosmic Strings
  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.
