Inferring the cosmological constant in early Universe only by gravitational waves

TL;DR

This paper explores how gravitational waves from primordial black hole mergers in the early universe can be used to infer the cosmological constant, demonstrating LISA's potential to constrain this fundamental parameter.

Contribution

It introduces a novel method to estimate the cosmological constant using gravitational wave signals from primordial black holes at high redshifts.

Findings

Binary PBHs with 1000 solar masses and z>500 are optimal for studying the cosmological constant.

LISA can effectively constrain the cosmological constant using these gravitational wave signals.

Abstract

The expansion of the Universe is accelerating which can be interpreted as due to the cosmological constant $\Lambda$. In this study, we investigate the behavior of gravitational waves in the presence of a cosmological constant in the early universe. We rigorously analyze the merger rate of binary primordial black holes (PBHs) and the corresponding signal-to-noise ratio within the framework of Laser Interferometer Space Antenna (LISA). We find that binary PBHs with a total mass of $M_{\mathrm{tot}}=1000M_{\odot}$ and a redshift larger than $z=500$ are the ideal system for studying the effect of the cosmological constant through LISA. By computing the fisher information matrix, we establish that the cosmological constant can be effectively constrained.