Constraining the stochastic gravitational wave from string cosmology with current and future high frequency detectors

TL;DR

This paper evaluates how current and future high-frequency gravitational wave detectors, including a proposed Chinese detector, can constrain the stochastic gravitational wave background predicted by string cosmology, showing significant improvements with new detector configurations.

Contribution

It analyzes the impact of detector network configurations, especially the addition of a Chinese detector and kilohertz sensitivity, on constraining string cosmology gravitational wave backgrounds.

Findings

Chinese detector improves detection prospects

Kilohertz detectors outperform previous detectors

Detector network constraints are limited by BBN bounds

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.