Search for the Gravitational-wave Background from Cosmic Strings with the Parkes Pulsar Timing Array Second Data Release

Abstract We perform a direct search for an isotropic stochastic gravitational-wave background (SGWB) produced by cosmic strings in the Parkes Pulsar Timing Array (PPTA) Data Release 2 (DR2). find no evidence such SGWB, and therefore place 95% confidence level upper limit on string tension, G ? , as function of reconnection probability, p which can be less than 1 string-theory-inspired models or pure Yang–Mills theory. The bound tension is ? 5.1 × 10 ?10 = 1, about five orders magnitude tighter derived from null individual bursts cusps PPTA DR2, comparable to previous bounds SGWB strings.