Cosmic String Interpretation of NANOGrav Pulsar Timing Data
  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.
