Constraining Cosmological Phase Transitions with Chinese Pulsar Timing Array Data Release 1

Abstract: The Chinese Pulsar Timing Array (CPTA) collaboration has recently reported the observational evidence of a stochastic gravitational wave background. In light of the latest CPTA observation, we aim at exploring the ability of CPTA in probing new physics. Specifically, we constrain the first-order cosmological phase transitions with CPTA data, and find that the constraining result is slightly tighter than that of NANOGrav's 12.5-yr data but weaker than NANOGrav's 15-yr data. Considering the possible complexity of gravitational wave sources, we give the constraint on a mixed scenario of cosmological phase transitions and astrophysical supermassive binary black holes. Our analysis suggests that CPTA has a great potential to probe fundamental physics in the near future.