Decay of Cosmic Global String Loops

Abstract

We numerically study the decay of cosmic global string loops due to radiation of Goldstone bosons and massive scalar ($\chi$) particles. The length of loops we study range from 200-1000 times the width of the string core. We find that the lifetime of a loop is $\approx 1.4L$. The energy spectrum of Goldstone boson radiation has a $k^{-1}$ fall off, where $k$ is the wavenumber, and a sharp peak at $k\approx m_{\chi }/2$, where $m_{\chi }$ is the mass of $\chi$. The latter is a new feature and implies a peak at high energies (MeV-GeV) in the cosmological distribution of QCD axions.

8 pages; 10 figures; An animation of a representative loop can be seen at https://ayushsaurabh.home.blog/2020/01/02/decay-of-cosmic-global-string-loops/