Cosmic String Interpretation of NANOGrav Pulsar Timing Data

TL;DR

This paper interprets the recent NANOGrav pulsar timing data as evidence for a stochastic gravitational wave background generated by cosmic strings, suggesting specific string tension values and implications for future detectors.

Contribution

It provides a cosmic string interpretation of the NANOGrav signal, linking it to specific string tension values and predicting detectability by upcoming gravitational wave observatories.

Findings

NANOGrav signal consistent with cosmic string SGWB

String tension estimated at Gμ in (4×10⁻¹¹, 10⁻¹⁰)

Future detectors could observe the predicted SGWB

Abstract

Pulsar timing data used to provide upper limits on a possible stochastic gravitational wave background (SGWB). However, the NANOGrav Collaboration has recently reported strong evidence for a stochastic common-spectrum process, which we interpret as a SGWB in the framework of cosmic strings. The possible NANOGrav signal would correspond to a string tension $G\mu \in (4 \times 10^{-11}, 10^{-10}) $ at the 68% confidence level, with a different frequency dependence from supermassive black hole mergers. The SGWB produced by cosmic strings with such values of $G\mu$ would be beyond the reach of LIGO, but could be measured by other planned and proposed detectors such as SKA, LISA, TianQin, AION-1km, AEDGE, Einstein Telescope and Cosmic Explorer.