Probing cosmic superstrings with gravitational waves
Abstract
We compute the stochastic gravitational wave background generated by cosmic superstrings using a semianalytical velocitydependent model to describe their dynamics. We show that heavier string types may leave distinctive signatures on the stochastic gravitational wave background spectrum within the reach of present and upcoming gravitational wave detectors. We examine the physically motivated scenario in which the physical size of loops is determined by the gravitational backreaction scale and use NANOGrav data to derive a conservative constraint of G μ_{F}<3.2 ×10^{9} on the tension of fundamental strings. We demonstrate that approximating the gravitational wave spectrum generated by cosmic superstring networks using the spectrum generated by ordinary cosmic strings with reduced intercommuting probability (which is often done in the literature) leads, in general, to weaker observational constraints on G μ_{F}. We show that the inclusion of heavier string types is required for a more accurate characterization of the region of the (g_{s},G μ_{F}) parameter space that may be probed using direct gravitational wave detectors. In particular, we consider the observational constraints that result from NANOGrav data and show that heavier strings generate a secondary exclusion region of parameter space.
 Publication:

Physical Review D
 Pub Date:
 September 2016
 DOI:
 10.1103/PhysRevD.94.063529
 arXiv:
 arXiv:1606.05585
 Bibcode:
 2016PhRvD..94f3529S
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 17 pages, 7 figures