Coherent Gravitational Waveforms and Memory from Cosmic String Loops

Understand

We construct, for the first time, the time-domain gravitational wave strain waveform from the collapse of a strongly gravitating Abelian Higgs cosmic string loop in full general relativity.

• We show that the strain exhibits a large memory effect during merger, ending with a burst and the characteristic ringdown as a black hole is formed.
• Furthermore, we investigate the waveform and energy emitted as a function of string width, loop radius and string tension $G\mu$.
• We find that the mass normalized gravitational wave energy displays a strong dependence on the inverse of the string tension $E_{\mathrm{GW}}/M_0\propto 1/G\mu$, with $E_{\mathrm{GW}}/M_0 \sim {\cal O}(1)\%$ at the percent level, for the regime where $G\mu\gtrsim10^{-3}$.