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

TL;DR

This work investigates sign-changeable interactions between vacuum energy and cold dark matter by adopting a running coupling $b(a)=b_0 a+b_e(1-a)$ and testing six interaction forms $Q(a)$, yielding IΛCDM1–IΛCDM6 models. Using a joint SN+CMB+BAO+$H_0$ analysis with Planck distance priors and JLA data, the authors constrain the parameters via MCMC, finding $b_0<0$ and $b_e>0$ at ~1σ and a strong anti-correlation between them. The reconstructed $b(z)$ crosses the noninteracting line $b=0$ around $z oughly0.2$–$0.3$ (≈0.6 for one model), indicating energy transfer from DM to DE during DM-dominated epochs and from DE to DM during DE-dominated epochs. All six models fit the data with similar χ², supporting the sign-changeable interaction scenario and extending earlier results with a broader set of $Q(a)$ forms and current observations.

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) $Q(a)=b(a)H_0ρ_0$, (ii) $Q(a)=b(a)H_0ρ_{\rm de}$, (iii) $Q(a)=b(a)H_0ρ_{\rm c}$, (iv) $Q(a)=b(a)Hρ_0$, (v) $Q(a)=b(a)Hρ_{\rm de}$, and (vi) $Q(a)=b(a)Hρ_{\rm c}$. 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$σ$ 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$σ$ 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.

Figures (3)

• Figure 1: The 1 $\sigma$ and 2 $\sigma$ confidence level contours in the $b_0$--$b_e$ plane, for the six I$\Lambda$CDM models, by using CMB+BAO+SN+$H_{0}$.
• Figure 2: The 1$\sigma$ and 2$\sigma$ confidence level contours in the $\Omega_m$--$h$ plane, for the six I$\Lambda$CDM models, by using CMB+BAO+SN+$H_{0}$.
• Figure 3: The reconstructed evolutionary histories for $b(z)$ in the six I$\Lambda$CDM models. The black solid line represents the 1$\sigma$ uncertainties. The blue dashed line in each plot denotes the noniteracting line.