Constraining the dark matter-vacuum energy interaction using the EDGES 21-cm absorption signal

TL;DR

This work addresses the EDGES 21-cm absorption tension with $\Lambda$CDM by testing a dark matter–vacuum energy interaction, introducing a coupling $Q=3\alpha H \frac{\rho_{\rm dm} V}{\rho_{\rm dm}+V}$ with a time-varying $\alpha(a)=\alpha_0+\alpha_a(1-a)$. By modifying the expansion history $H(z)$ and incorporating it into the 21-cm observable $T_{21}$, the authors perform a joint cosmological parameter estimation using EDGES alongside Planck CMB, SNe, BAO, RSD, and $H_0$ data. They find that EDGES alone strongly favors an interacting vacuum model (>99% CL) and marginally tightens constraints on $\alpha_0$ and $\alpha_a$, while the combined dataset remains consistent with $\Lambda$CDM at 68% CL and yields about a 10% improvement in the Figure of Merit. The results demonstrate the potential of upcoming 21-cm experiments to constrain interacting dark energy models and motivate future, more precise measurements (e.g., SKA) to probe the dark sector, subject to systematic uncertainties.

Abstract

The recent measurement of the global 21-cm absorption signal reported by the Experiment to Detect the Global Epoch of Reionization Signature (EDGES) Collaboration is in tension with the prediction of the $Λ$CDM model at a $3.8\,σ$ significance level. In this work, we report that this tension can be released by introducing an interaction between dark matter and vacuum energy. We perform a model parameter estimation using a combined dataset including EDGES and other recent cosmological observations, and find that the EDGES measurement can marginally improve the constraint on parameters that quantify the interacting vacuum, and that the combined dataset favours the $Λ$CDM at 68\% CL. This proof-of-the-concept study demonstrates the potential power of future 21-cm experiments to constrain the interacting dark energy models.

Figures (5)

• Figure 1: The dashed lines of $\alpha_0=0$ and $\alpha_0+\alpha_a=0$ divide the parameter space of $\alpha_0$ and $\alpha_a$ into four regions, where $w_V^{\rm eff}$ is greater than $-1$ in the past and smaller than $-1$ today in the models of "Quintom-like A", while $w_V^{\rm eff}$ crosses $-1$ from the values smaller than $-1$ to that greater than $-1$ in the models of "Quintom-like B". The black star denotes the $\Lambda$CDM model.
• Figure 2: Upper panel: The cosmic expansion rate and Compton-heating rate in the $\Lambda$CDM and interacting vacuum energy model with fixed parameters i.e.$\alpha_0=-0.5$ and $\alpha_a=0$. Lower panel: CMB temperature and gas temperatures in the $\Lambda$CDM and interacting vacuum energy model with fixed parameters i.e.$\alpha_0=-0.5$ and $\alpha_a=0$.
• Figure 3: An illustration of the intensity of the 21-cm signal relative to the CMB temperature, $T_{21}(\rm K)$, for various values of $\alpha_0$ and $\alpha_a$. The colour bar indicates the values of $\alpha_a$. The black solid curve corresponds to the case in which $\alpha$ does not evolve with time ($\alpha_a=0)$. The intersect between the black solid curve and the vertical grey dashed line, marked by a yellow star, denotes the $\Lambda$CDM model. The hatched region illustrates the observed 21-cm signal from EDGES at 99% CL.
• Figure 4: The contour plots for parameters $\{\alpha_0, \alpha_a\}$ derived from different data combinations including EDGES alone (shaded regions and solid curves in the left corner; the solid curves from left to right denote 68, 95 and 99% CL contours respectively), CMB + SNe + BAO + RSD + $H_0$ (blue dashed), and CMB + SNe + BAO + RSD + $H_0$ + EDGES (solid green). The yellow star marks the $\Lambda$CDM model. The dashed lines denote $\alpha_0=0$ and $\alpha_0+\alpha_a=0$, which divide the $\alpha_0$-$\alpha_a$ parameter space into four regions, as illustrated in Fig. \ref{['fig:scalar_field_like']}.
• Figure 5: The 68 and 95% CL parametric reconstruction of $\alpha(a)$ using CMB+SNe+BAO+RSD+$H_0$ with (right) and without (left) the EDGES measurement.