Anisotropies in the gravitational wave background as a probe of the cosmic string network

Abstract

Pulsar timing arrays are powerful tools to test the existence of cosmic strings by searching for the gravitational wave (GW) background. The amplitude of the background connects to information on cosmic strings such as the tension and string network properties. In addition, one may be able to extract more information on the properties of cosmic strings by measuring anisotropies in the GW background. In this paper, we provide estimates of the level of anisotropy expected in the GW background generated by cusps on cosmic strings. We find that the anisotropy level strongly depends on the initial loop size $\ensuremath{\alpha}$, and thus we may be able to put constraints on $\ensuremath{\alpha}$ by measuring the anisotropy of the GW background. We also find that certain regions of the parameter space can be probed by shifting the observation frequency of GWs.