http://arxiv.org/abs/2107.01845
Stochastic gravitational wave background (SGWB) is a promising tool to probe the very early universe where the standard model of particle physics and cosmology are connected closely. As a possible component of SGWB, gravitational waves (GW) from bubble collisions during the first order cosmological phase transitions deserve comprehensive analyses. In 2017, Ryusuke Jinno and Masahiro Takimoto proposed an elegant analysis approach to derive the analytical expressions of energy spectra of GW from bubble collisions in Minkowski spacetime avoiding large-scale numerical simulations for the first time[1]. However, they neglect the expansion of the universe and regard the duration of phase transitions as infinity in their derivation which could deviate their estimations from true values. For these two reasons, we give a new expression of GW spectra by adopting their method, switching spacetime background to FLRW spacetime and considering a finite duration of phase transitions. By denoting $\sigma$ as the fraction of the speed of phase transitions to the expansion speed of the universe, we find for different $\sigma$, the maxima of GW energy spectra drop by around 1-3 orders of magnitude than the results given by their previous work. Such a significant decrease may bring about new challenges for detectability of GW from bubble collisions. Luckily, by comparing new spectra with PLI (power-law integrated) sensitivity curves of GW detectors, we find GW from bubble collisions still could be detectable for BBO and LISA in future detection.
H. Zhong, B. Gong and T. Qiu
Thu, 8 Jul 21
14/52
Comments: 16 pages, 8 figures