Search for stochastic gravitational-wave background from string cosmology with Advanced LIGO and Virgo's O1?O3 data

String cosmology models predict a relic background of gravitational-wave (GW) radiation in the early universe. The GW energy spectrum of radiated power increases rapidly with the frequency, and therefore it becomes a potential and meaningful observation object for high-frequency GW detector. We focus on the stochastic background generated by su-p erinflation in string theory and search for such signal in the observing data of Advanced LIGO and Virgo O1 similar to O3 runs in a Bayesian framework. We do not find the existence of the signal, and thus put constraints on the GW energy density. Our results indicate that at f = 100 Hz, the fractional energy density of GW background is less than 1.7 x 10-8 and 2.1 x 10-8 for dilaton-string and dilaton only cases respectively, and further rule out the parameter space restricted by the model itself due to the non-decreasing dilaton and stable cosmology background (0 bound).

Automated summary

Cosmology models predict a relic background of gravitational-wave radiation in the early universe. Using a Bayesian framework, we focused on the stochastic background generated by superinflation in string theory and searched for this signal in the observing data of Advanced LIGO and Virgo O1 to O3 runs. Our results put constraints on the GW energy density, ruling out certain parameter space restricted by the model itself due to non-decreasing dilaton and stable cosmology background (0 bound).