Probing Spin-2 Ultralight Dark Matter with Space-based Gravitational Wave Detectors in the mHz Regime

TL;DR

This paper explores how space-based gravitational wave detectors can detect or constrain spin-2 ultralight dark matter by analyzing their response functions and sensitivity, potentially surpassing current limits.

Contribution

It introduces a method to use space-based GW detectors to probe spin-2 ULDM, deriving response functions and sensitivity curves for future millihertz detectors.

Findings

Space-based detectors can constrain the coupling constant to $ ext{~}10^{-10}$.

Detectors can surpass current ground-based and pulsar timing limits.

Potential to probe fundamental properties of ultralight dark matter.

Abstract

Spin-2 ultralight dark matter (ULDM) is a viable dark matter candidate and it can be constrained using gravitational wave (GW) observations. In this paper, we investigate the detectability of spin-2 ULDM by space-based GW interferometers. By considering a direct coupling between spin-2 ULDM and ordinary matter, we derive the corresponding response functions and sensitivity curves for various time-delay interferometry channels and calculate the optimal sensitivity curves for future millihertz GW detectors. Our results demonstrate that the space-based detectors can place stringent constraints on the coupling constant of spin-2 ULDM, reaching $\alpha \sim 10^{-10}$ around a mass of $m \sim 10^{-17} \rm eV$, surpassing current limits from ground-based detectors and pulsar timing arrays. Thus, the space-based GW detectors can serve as powerful tools not only for detecting GWs but also for probing fundamental properties of ultralight dark matter.