Late-time entropy production due to the decay of domain walls

Abstract

It is shown that late-time decay of domain walls can dilute unwanted relics such as moduli, if the universe was dominated by frustrated domain walls with tension $\sigma = (1 - 100 TeV)^3$. Since energy density of the frustrated domain walls decreases as slow as the inverse of the scale factor, an overclosure limit on the axion decay constant $f_a$ is also considerably relaxed. In fact $f_a$ can be as large as the Planck scale, which may enable us to naturally implement the QCD axion in the string scheme. Furthermore, in contrast to thermal inflation models, the Affleck-Dine baryogenesis can generate enough asymmetry to explain the present baryon abundance, even in the presence of late-time entropy production.