2025/04/23 by Huang, Fan, Chen, Zu-Cheng, Huang, Qing-Guo
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Instrumentation and Methods for Astrophysics (astro-ph.IM)
paper · doi:10.48550/arxiv.2504.16712
We investigate the capability of the Taiji space-based gravitational wave observatory to detect stochastic gravitational wave backgrounds produced by first-order phase transitions in the early universe. Using a comprehensive simulation framework that incorporates realistic instrumental noise, galactic double white dwarf confusion noise, and extragalactic compact binary backgrounds, we systematically analyze Taiji's sensitivity across a range of signal parameters. Our Bayesian analysis demonstrates that Taiji can robustly detect and characterize phase transition signals with energy densities exceeding ΩPT \gtrsim 1.4 × 10-11 across most of its frequency band, with particularly strong sensitivity around 10-3 to 10-2 Hz. For signals with amplitudes above ΩPT \gtrsim 1.1 × 10-10, Taiji can determine the peak frequency with relative precision better than 10%. These detection capabilities would enable Taiji to probe electroweak-scale phase transitions in various beyond-Standard-Model scenarios, potentially revealing new physics connected to baryogenesis and dark matter production. We quantify detection confidence using both Bayes factors and the Deviance Information Criterion, finding consistent results that validate our statistical methodology.