Has NANOGrav found first evidence for cosmic strings?
  The North American Nanohertz Observatory for Gravitational Waves (NANOGrav)
has recently reported strong evidence for a stochastic common-spectrum process
affecting the pulsar timing residuals in its 12.5-year data set. We demonstrate
that this process admits an interpretation in terms of a stochastic
gravitational-wave background emitted by a cosmic-string network in the early
Universe. We study stable Nambu-Goto strings in dependence of their tension
$G\mu$ and loop size $\alpha$ and show that the entire viable parameter space
will be probed by an array of future experiments.
