Probing the sign-changeable interaction between dark energy and dark matter with current observations

TL;DR

This study investigates models where the interaction between dark energy and dark matter can change sign over time, using current observational data to constrain the parameters and reveal the nature of their energy exchange.

Contribution

It introduces a parameterization of the sign-changing coupling between dark energy and dark matter and constrains it with multiple observational datasets.

Findings

Coupling parameters show strong anti-correlation.

Sign change in coupling occurs around the transition from matter to dark energy domination.

Energy transfer direction reverses during cosmic evolution.

Abstract

We consider the models of vacuum energy interacting with cold dark matter in this study, in which the coupling can change sigh during the cosmological evolution. We parameterize the running coupling $b$ by the form $b(a)=b_0a+b_e(1-a)$, where at the early-time the coupling is given by a constant $b_{e}$ and today the coupling is described by another constant $b_{0}$. We explore six specific models with (i) $Q(a)=b(a)H_0\rho_0$, (ii) $Q(a)=b(a)H_0\rho_{\rm de}$, (iii) $Q(a)=b(a)H_0\rho_{\rm c}$, (iv) $Q(a)=b(a)H\rho_0$, (v) $Q(a)=b(a)H\rho_{\rm de}$, and (vi) $Q(a)=b(a)H\rho_{\rm c}$. The current observational data sets we use to constrain the models include the JLA compilation of type Ia supernova data, the Planck 2015 distance priors data of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the Hubble constant direct measurement. We find that, for all the models, we have $b_0<0$ and $b_e>0$ at around the 1$\sigma$ level, and $b_0$ and $b_e$ are in extremely strong anti-correlation. Our results show that the coupling changes sign during the evolution at about the 1$\sigma$ level, i.e., the energy transfer is from dark matter to dark energy when dark matter dominates the universe and the energy transfer is from dark energy to dark matter when dark energy dominates the universe.