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