分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2023-07-25
摘要: Strong evidence for a gravitational-wave background (GWB) has been reported in the nano-Hertz band. Interpreting the origin of this background to be scalar-induced gravitational waves (SIGWs), we explore the equation of state (EoS) of the early universe by performing Bayes parameter inferences across the big-bang nucleosynthesis (BBN), cosmic microwave background (CMB), and pulsar timing array (PTA) joint observations for the first time. Assuming a monochromatic power spectrum for primordial curvature perturbations, we obtain the spectral amplitude A\sim10^{-3}-10^{-1} and spectral peak frequency f_\ast\sim10^{-7}-10^{-6} Hz. We find that the radiation domination with EoS w=1/3 is compatible with the current observational data, the kination domination with EoS w=1 is not forbidden, while the early matter domination with EoS w=0 is excluded at more than 2\sigma confidence level. These results can be tested with future observations.