Abstract
Abstract Pre–Big Bang models in string cosmology predict a relic background of gravitational wave radiation in the early universe. The spectrum of this background shows that the energy density rises rapidly with frequency, which is an interesting target for high-frequency (i.e., kilohertz) detectors. In this paper, we discussed the constraining power of multiple configurations of current and future gravitational wave detector (GWD) networks to the stochastic background predicted in string cosmology. The constraining power is jointly determined by the overlap reduction function and the sensitivity curves of multiple detectors. And we further elaborated on the possible contribution of a future Chinese detector and a kilohertz detector to the constraining power of detector network for stochastic background in string cosmology. Our results show that the detectability of the GWD network for the string cosmology gravitational wave background will improve considerably with the joining of a Chinese detector. This is because a Chinese detector (e.g., located at Wuhan), together with KAGRA, has a better overlap reduction function than the laser interferometer gravitational wave observatory detector pair, and therefore lead to more stringent limits for stochastic background detection. And with ideal overlap reduction function, namely, colocated detectors, a kilohertz sensitivity curve has better performance than previous detectors for stochastic background detection. Finally, the results are compared with the limitations given by the observational constraint of the Big Bang nucleosynthesis bound.
Highlights
The standard cosmological model gives a very good explanation of the present universe, but its universality has been hit by intractable difficulties in explaining the initial singularity (Gasperini & Veneziano 1993)
Considering the sensitivity curve of Laser Interferometer Gravitational-Wave Observatory (LIGO) detector pairs is better than that of KAGRA-CKGO, it indicates that KAGRA-CKGO has a much better overlap reduction function than that of LIGO detector pairs, and the combined effect leads to KAGRA-CKGO making a big contribution to the second generation detector network for stochastic background detection
If the sensitivity curve of LIGO voyager is applied to KAGRA and CKGO, the results will turn out to be that KAGRA-CKGO have better performance than LIGO detector pairs
Summary
The detectability for string cosmology inevitably depends on the sensitivity and co-response of GWDs. On 2019 April 1st, astronomers and physicists around the world welcomed a long-awaited moment: LIGO in the United States and the Virgo Interferometer in Europe, both of which have significantly improved their detection sensitivity, have officially launched the third run of the year-long gravitational wave experiment (O3). Once operating along with the existing GW detectors, KAGRA will be helpful in locating GW sources more accurately and determining the source parameters with higher precision, improving the detectability of the detector network (Akutsu et al 2018) In this context, China is expected to establish a ground-based GWD in the near future. China is expected to establish a ground-based GWD in the near future This will naturally lead to a problem: how much contribution will the GWD in China (CGWD) make to the detector network for stochastic background detection?
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