On the Possible Enhancement of the Global $21$-cm Signal at Reionization from the Decay of Cosmic String Cusps

Understand

We consider cosmic string cusp annihilations as a possible source of enhancement to the global background radiation temperature in $21$-cm photons at reionization.

• A soft photon spectrum is induced via the Bremsstrahlung and Synchrotron emission of electrons borne out of QCD jets formed off the cusp.
• The maximal energy density background comes from synchrotron induced photons with a string tension of $G\mu \sim 10^{-18}$.
• In this instance, the radiation background at reionization is heated up by $5\cdot 10^{-3} \,\, K$.