Prospects for Taiji to detect a gravitational-wave background from cosmic strings

Abstract

Recently, multiple pulsar timing array collaborations have presented compelling evidence for a stochastic signal at nanohertz frequencies, potentially originating from cosmic strings. Cosmic strings are linear topological defects that can arise during phase transitions in the early Universe or as fundamental strings in superstring theory. This paper focuses on investigating the detection capabilities of Taiji, a planned space-based gravitational wave detector, for the gravitational wave background generated by cosmic strings. By analyzing simulated Taiji data and utilizing comprehensive Bayesian parameter estimation techniques, we demonstrate a significant improvement in precision compared to the NANOGrav 15-year data set, surpassing it by an order of magnitude. This highlights the enhanced measurement capabilities of Taiji. Consequently, Taiji can serve as a valuable complementary tool to pulsar timing arrays in validating and exploring the physics of cosmic strings in the early Universe.

The Pulsar Timing Array Signal from Infrared Regions of Scalar-Induced Gravitational Waves

“…7 −0.6 × 10 −15 at a reference frequency of 1 yr −1 [86]. While supermassive black hole binaries are considered as an explanation [93][94][95][96][97][98][99], alternative interpretations include cosmic inflation [94,95], first-order phase transitions [100][101][102][103][104][105][106][107], cosmic strings [108][109][110][111][112][113][114][115], domain walls [116][117][118], or scalar-induced gravitational waves [4,[119][120][121][122][123][124][125][126][127][128][129][130][131]. For more about the physical explanation of signals in the PTA band, please refer to the references [132][133][134]…”