Interacting scenarios with dynamical dark energy: observational constraints and alleviation of the $H_0$ tension

TL;DR

This work investigates interacting dark energy models with a dynamical one-parameter equation of state, implemented via the coupling $Q = 3 \xi H (1+w_x) \rho_x$ across four parametrizations IDE1–IDE4. By confronting these models with Planck 2015 CMB, JLA, BAO, CC, and SH0ES $H_0$ priors, the authors find the coupling $\xi$ is generally small and compatible with zero within 2$\sigma$, while the current dark-energy equation of state remains phantom ($w_0<-1$) and anti-correlated with $H_0$. Importantly, for all IDE models the inferred $H_0$ values are higher than the Planck $\Lambda$CDM estimate and closer to local measurements, thus mitigating the $H_0$ tension to roughly $2$–$3\sigma$ depending on the data combination. Bayesian evidence mostly favors $\Lambda$CDM, except when the SH0ES prior is included, where the IDE scenarios show weak to positive support. Overall, the study demonstrates that extended interacting scenarios with a dynamical dark-energy component can alleviate the $H_0$ tension without requiring a substantial nonzero coupling, highlighting a promising direction for precision cosmology.

Abstract

We investigate interacting scenarios which belong to a wider class, since they include a dynamical dark energy component whose equation of state follows various one-parameter parametrizations. We confront them with the latest observational data from Cosmic Microwave Background (CMB), Joint light-curve (JLA) sample from Supernovae Type Ia, Baryon Acoustic Oscillations (BAO), Hubble parameter measurements from Cosmic Chronometers (CC) and a gaussian prior on the Hubble parameter $H_0$. In all examined scenarios we find a non-zero interaction, nevertheless the non-interacting case is allowed within 2$σ$. Concerning the current value of the dark energy equation of state for all combination of datasets it always lies in the phantom regime at more than two/three standard deviations. Finally, for all interacting models, independently of the combination of datasets considered, the estimated values of the present Hubble parameter $H_0$ are greater compared to the $Λ$CDM-based Planck's estimation and close to the local measurements, thus alleviating the $H_0$ tension.

Figures (9)

• Figure 1: The 68% and 95% Confidence Level (CL) contour plots between various combinations of the model parameters of scenario IDE1, using different observational astronomical datasets. Additionally we display the one-dimensional marginalized posterior distributions of some free parameters.
• Figure 2: The 68% and 95% CL contour plots between various combinations of the model parameters of scenario IDE1 using only the CMB+BAO and CMB+BAO+R19 datasets, and the corresponding one-dimensional marginalized posterior distributions.
• Figure 3: Whisker plot with the 68% CL constraints on the Hubble constant for all interacting models and all combination of datasets considered in this work. The grey vertical band corresponds to the R19 value for the Hubble constant, $H_0$, as measured by SH0ES in Riess:2019cxk, and the red vertical band is the one estimate by the Planck 2018 release Aghanim:2018eyx.
• Figure 4: The 68% and 95% CL contour plots between various combinations of the model parameters of scenario IDE2, using different observational astronomical datasets. Additionally we display the one-dimensional marginalized posterior distributions of some free parameters.
• Figure 5: The 68% and 95% CL contour plots between various combinations of the model parameters of scenario IDE2 using only the CMB+BAO and CMB+BAO+R19 datasets, and the corresponding one-dimensional marginalized posterior distributions.