Listening to the sound of dark sector interactions with gravitational wave standard sirens

TL;DR

This paper investigates how gravitational wave standard sirens from the Einstein Telescope can sharpen constraints on dark sector interactions between dark matter and dark energy, within two stable IDE models (IDErc1 and IDErc2). By generating mock GW distance measurements and combining them with Planck CMB data in an 8-parameter cosmology including the coupling ξ, the authors forecast substantial improvements in parameter constraints. They find that GW data can reduce uncertainties on the DM–DE coupling by up to a factor of ~5 and could elevate the statistical significance of a nonzero ξ beyond 3σ if such an interaction exists within current limits. The work demonstrates the potential of next-generation gravitational wave observations to probe dark sector physics and informs future multi-messenger cosmology, while highlighting caveats and avenues for refinement and broader applicability.

Abstract

We consider two stable Interacting Dark Matter -- Dark Energy models and confront them against current Cosmic Microwave Background data from the \textit{Planck} satellite. We then generate luminosity distance measurements from ${\cal O}(10^3)$ mock Gravitational Wave events matching the expected sensitivity of the proposed Einstein Telescope. We use these to forecast how the addition of Gravitational Wave standard sirens data can improve current limits on the Dark Matter -- Dark Energy coupling strength ($ξ$). We find that the addition of Gravitational Waves data can reduce the current uncertainty by a factor of $5$. Moreover, if the underlying cosmological model truly features Dark Matter -- Dark Energy interactions with a value of $ξ$ within the currently allowed $1σ$ upper limit, the addition of Gravitational Wave data would help disentangle such an interaction from the standard case of no interaction at a significance of more than $3σ$.

Figures (4)

• Figure 1: Mock $d_L(z)$ measurements resulting from 1000 simulated GW events assuming a fiducial IDErc1 model (left panel) and IDErc2 model (right panel). The fiducial cosmological parameters are the best-fit values obtained when constraining these models against CMB data alone, except for $\xi$ which is fixed to $\xi=0.01$ and $\xi=0.025$ for the IDErc1 and IDErc2 models respectively.
• Figure 2: 1D marginalized and 2D joint posterior distributions for selected parameters (including a selection of derived parameters) of the IDErc1 model whose determination is particularly improved by the inclusion of the GW dataset: $w_x$, $\xi$, $\Omega_{m0}$ (the total matter density parameter today), $\sigma_8$, and $H_0$ (in ${\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$). Contours are obtained using only CMB data (grey) and CMB+GW data (red).
• Figure 3: 1D marginalized and 2D joint posterior distributions comparing the CMB+BAO case (red contours) with CMB+GW (green contours), for selected parameters (including a selection of derived parameters), assuming the IDErc1 model.
• Figure 4: As in Fig. \ref{['fig:IDErc1']}, for the IDErc2 model.