A New Window on Dynamical Dark Energy: Combining DESI-DR2 BAO with future Gravitational Wave Observations

Abstract

Baryon acoustic oscillation (BAO) data from the Dark Energy Spectroscopic Instrument (DESI) appear to indicate the first evidence for dynamical dark energy (DDE), with a present-day behavior resembling quintessence. This evidence emerges when the Chevallier-Polarski-Linder (CPL) parameterization of the dark energy equation of state, $w_{\textrm{de}} = w_0 + w_a (1-a)$, is considered, and persists across other functional forms of $w_{\textrm{de}}$. In this work, we investigate how the inclusion of future gravitational wave (GW) standard siren data impacts the uncertainties in cosmological parameters when combined with DESI measurements. Specifically, we analyze the expected contributions from upcoming GW observatories such as the Einstein Telescope (ET) and the Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO), as well as the current Laser Interferometer Gravitational-Wave Observatory (aLIGO). We find that the addition of GW data, particularly from DECIGO, significantly reduces the uncertainties in cosmological parameters, with the extent of the improvement depending on the specific form of $w_{\textrm{de}}$ and being more expressive for the $Ω_m$ and $H_0$ parameters for all models studied. Our results highlight both the constraining power of future GW observations and the importance of considering a range of cosmological models in the data analysis.