Axions from wall decay

Abstract

We discuss the decay of axion walls bounded by strings and present numerical simulations of the decay process. In these simulations, the decay happens immediately, in a time scale of order the light travel time, and the average energy of the radiated axions is $<\omega_a > \simeq 7 m_a$ for $v_a/m_a\simeq 500$. $<\omega_a>$ is found to increase approximately linearly with $\ln(v_a/m_a)$. Extrapolation of this behaviour yields $<\omega_a> \simeq 60 m_a$ in axion models of interest.