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

TL;DR

This study searches for a high-frequency stochastic gravitational-wave background predicted by string cosmology models using Advanced LIGO and Virgo data, setting upper limits on the energy density and constraining model parameters.

Contribution

First to analyze LIGO and Virgo O1–O3 data for stochastic GW background from string cosmology, providing new constraints on model parameters and the GW energy density.

Findings

No detection of the predicted GW background.

Upper limits on GW energy density at 100 Hz: less than 1.7×10⁻⁸ and 2.1×10⁻⁸.

Constraints on string cosmology model parameters.

Abstract

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 superinflation in string theory and search for such signal in the observing data of Advanced LIGO and Virgo O1$\sim$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 $f=100\,\text{Hz}$, the fractional energy density of GW background is less than $1.7\times10^{-8}$ and $2.1\times10^{-8}$ 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 ($\beta$ bound).