Cosmic Equation of State and Advanced LIGO Type Gravity Wave Experiments

Abstract

Future generation of interferometric gravitational wave detectors is hoped to provide accurate measurements of the final stages of binary inspirals. The sources probed by such experiments are of extragalactic origin and the observed chirp mass is the intrinsic chirp mass multiplied by $(1+z)$ where $z$ is the redshift of the source. Moreover the luminosity distance is a direct observable is such experiments. This creates the possibility to establish a new kind of cosmological tests, supplementary to more standard ones. Recent observations of distant type Ia supernovae light-curves suggest that the expansion of the universe has recently begun to accelerate. A popular explanation of present accelerating expansion of the universe is to assume that some part $Ω_Q$ of the matter-energy density is in the form of dark component called ``the quintessence'' with the equation of state $p_Q = w ρ_Q$ with $w \geq -1.$ In this paper we consider the predictions concerning observations of binary inspirals in future LIGO type interferometric experiments assuming a ``quintessence cosmology''. In particular we compute the expected redshift distributions of observed events in the a priori admissible range of parameters describing the equation of state for the quintessence. We find that this distribution has a robust dependence on the cosmic equation of state.