Comparison of cosmic string and superstring models to NANOGrav 12.5-year results

TL;DR

This paper compares cosmic string and superstring models' gravitational wave spectra with NANOGrav's recent observations, highlighting uncertainties and parameter dependencies, and assessing their viability as explanations for the observed signal.

Contribution

It provides a detailed comparison of cosmic string and superstring models against NANOGrav data, considering theoretical uncertainties and parameter constraints.

Findings

Cosmic strings can explain the NANOGrav signal within certain parameters.

Superstrings may explain the signal but only in restricted conditions.

Theoretical uncertainties affect the interpretation of the models.

Abstract

We compare the spectrum of the stochastic gravitational wave background produced in several models of cosmic strings with the common-spectrum process recently reported by NANOGrav. We discuss theoretical uncertainties in computing such a background, and show that despite such uncertainties, cosmic strings remain a good explanation for the potential signal, but the consequences for cosmic string parameters depend on the model. Superstrings could also explain the signal, but only in a restricted parameter space where their network behavior is effectively identical to that of ordinary cosmic strings.