Decay of Cosmic Global String Loops

We numerically study the decay of cosmic global string loops due to radiation of Goldstone bosons and massive scalar ($χ$) 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 $\approx 1.4 L$. The energy spectrum of Goldstone boson radiation has a $k^{-1}$ fall off, where $k$ is the wavenumber, and a sharp peak at $k \approx m_χ/2$, where $m_χ$ is the mass of $χ$. The latter is a new feature and implies a peak at high energies (MeV-GeV) in the cosmological distribution of QCD axions.

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