Axions from cosmic string and wall decay

Abstract

If inflation occurred with a reheat temperature > TPQ, axions from the decay of global axion strings and domain walls would make an important contribution to the cosmological energy density, comparable to that from vacuum misalignment. Several groups have numerically studied the evolution of axion strings and walls in the past, however substantial uncertainties remain in their contribution to the present density Ωa,string+wall∼1–100(fa/1012 GeV)7/6, where fa is the axion decay constant. I will describe the numerical methods used in our simulations and show results for several string and wall configurations.