Constraints on the interaction strength in the model of interacting dynamical dark energy with linear and non-linear interacting terms

TL;DR

This work tests three dynamical IDE models coupling dark energy and dark matter against CMB, BAO, and SN Ia data. Two models involve linear couplings proportional to the Hubble rate, while a novel non-linear, density-product coupling is analyzed for the first time. Using a Planck 2018–BAO–Pantheon dataset suite with an IDE-modified perturbation framework, the linear models are disfavored by local $H_0$ measurements and yield only upper limits on the coupling, whereas the non-linear model shows better agreement with local $H_0$ and provides >1σ evidence for a non-zero coupling. The results indicate that dynamical DE with DE–DM interaction can affect structure formation and $H_0$ inferences, motivating tighter constraints with forthcoming data.

Abstract

In this work the observational constraints on interaction coupling parameter between dynamical dark energy and cold dark matter were obtained using CMB, BAO and SN Ia data. The dark energy in considered models is dynamical and evolution of its equation of state parameter depends on dark coupling and internal properties of the dark energy. Such model is believed to be more physically consistent than models of interacting dark energy considered in previous works. Constraints were made for three types of interaction. The first two are the types which are often considered in other works on interacting dark energy. The third type has the non-linear dependence on densities of dark components and is studied for the first time. Observational constraints on Hubble constant $H_{0}$ for the first two models are in strong disagreement with so called local measurements of $H_{0}$. And the third model is in better agreement with local measurements than $Λ$CDM model. Also for the last non-linear model existence of non-zero interaction was found at greater than $1σ$ significance level.

Figures (2)

• Figure 1: Dependence of the matter power spectrum at redshift $z=0$ on the interaction parameter $\beta$ for Model I in the upper panel and for Model II in the lower panel. The independent model parameters that were used are as follows: $\Omega_{b}h^{2}=0.0226$, $\Omega_{c}h^{2}=0.112$, $H_{0}=68.2$, $\Omega_{K}=0$, $A_{s}=2.1\times10^{-9}$, $n_{s}=0.96$, $\tau=0.09$, $c_{s}^{2}=1$, $w_{0}=-0.9$, $c_{a}^{2}=-0.5$.
• Figure 2: Dependence of the matter power spectrum at redshift $z=0$ on the interaction parameter $\beta$ for Model III with $c_{a}^{2}=-0.5$ in the upper panel and $c_{a}^{2}=-1.2$ in the lower panel. The independent model parameters that were used are the same as in Fig. \ref{['fig:1']}.