21 cm Angular Spectrum of Cosmic String Loops

The 21 cm signatures induced by moving cosmic string loops are investigated. Moving cosmic string loops seed filamentary nonlinear objects. We analytically evaluate the differential 21 cm brightness temperature from these objects. We show that the brightness temperature reaches 200 mK for a loop whose tension is about the current upper limit, $G\mu\sim10^{-7}$. We also calculate the angular power spectrum, assuming scaling in loop distribution. We find that the angular power spectrum for $G\mu>10^{-8}$ at $z=30$ or $G\mu>10^{-10}$ at $z=20$ can dominate the spectrum of the primordial density fluctuations. Finally we show that a future SKA-like observation has the potential to detect the power spectrum due to loops with $G\mu=10^{-8}$ at $z=20$.