Comprehensive analysis of the tidal effect in gravitational waves and implication for cosmology

TL;DR

This paper analyzes how tidal effects in gravitational wave signals from neutron star mergers can be used to determine their redshifts and equation-of-state, significantly improving constraints on dark energy parameters in future detector networks.

Contribution

It provides a comprehensive analysis of using tidal effects in GW waveforms for cosmological parameter estimation and demonstrates the potential for much tighter constraints with 3G detectors.

Findings

GW observations can determine neutron star EOS with high precision.

Tidal effects enable redshift measurement of GW sources without electromagnetic counterparts.

Future GW detectors can constrain dark energy parameters orders of magnitude better than traditional methods.

Abstract

Detection of gravitational waves (GWs) produced by coalescence of compact binaries provides a novel way to measure the luminosity distance of GW events. Combining their redshift, they can act as standard sirens to constrain cosmological parameters. For various GW detector networks in 2nd-generation (2G), 2.5G and 3G, we comprehensively analyze the method to constrain the equation-of-state (EOS) of binary neutron-stars (BNSs) and extract their redshifts through the imprints of tidal effects in GW waveforms. We find for these events, the observations of electromagnetic counterparts in low-redshift range $z < 0.1$ are important for constraining the tidal effects. Considering 17 different EOSs of NSs or quark-stars, we find GW observations have strong capability to determine the EOS. Applying the events as standard sirens, and considering the constraints of NS's EOS derived from low-redshift observations as prior, we can constrain the dark-energy EOS parameters $w_0$ and $w_a$. In 3G era, the potential constraints are $\Delta w_0\in (0.0006,0.004)$ and $\Delta w_a\in(0.004,0.02)$, which are 1-3 orders smaller than those from traditional methods, including Type Ia supernovas and baryon acoustic oscillations. The constraints are also 1 order smaller than the method of GW standard siren by fixing the redshifts through short-hard $\gamma$-ray bursts, due to more available GW events in this method. Therefore, GW standard sirens, based on the tidal effect measurement, provide a realizable and much more powerful tool in cosmology.