Probing Dark Energy with Black Hole Binaries

TL;DR

This paper proposes a novel method to measure dark energy's equation of state by analyzing gravitational waves from supermassive black hole binaries, offering an alternative to large-scale surveys and providing insights into dark energy properties.

Contribution

It introduces a new approach using gravitational wave data from black hole binaries to directly probe dark energy's equation of state, complementing existing methods.

Findings

Gravitational waves from black hole binaries carry information about dark energy.

Orbital changes in binaries are influenced by dark energy accretion proportional to (1+w).

Method can potentially detect dark energy effects with current and future observatories.

Abstract

The equation of state (EoS) of dark energy $w$ remains elusive despite enormous experimental efforts to pin down its value and its time variation. Yet it is the single most important handle we have in our understanding of one of the most mysterious puzzle in nature, dark energy. This letter proposes a new method for measuring the EoS of dark energy by using the gravitational waves (GW) of black hole binaries. The method described here offers an alternative to the standard way of large scale surveys. It is well known that the mass of a black hole changes due to the accretion of dark energy but at an extremely slow rate. However, a binary of supermassive black holes (SBH) radiates gravitational waves with a power proportional to the masses of these accreting stars and thereby carries information on dark energy. These waves can propagate through the vastness of structure in the universe unimpeded. The orbital changes of the binary, induced by the energy loss from gravitational radiation, receive a large contribution from dark energy accretion. This contribution is directly proportional to $(1+w)$ and is dominant for SBH binaries with separation $R \ge 1000$ parsec, thereby accelerating the merging process for $w > -1$ or ripping the stars apart for phantom dark energy with $w < -1$. Such orbital changes, therefore $w$, can be detected with LIGO and LISA near merging time, or with X-ray and radio measurements of Chandra and VLBA experiments.