Testing the Interaction between Dark Energy and Dark Matter with Planck Data

TL;DR

The paper tests a phenomenological interaction between dark energy and dark matter against Planck CMB data using a coupling $Q=3H(\xi_1 ho_c+\xi_2 ho_d)$ and performs a global Bayesian analysis with Planck plus BAO, SNIa, and H0 constraints, allowing the dark energy equation of state $ ext{ω}$ to vary. It analyzes four coupling scenarios (Models I–IV) at background and linear perturbation levels, showing Model I favors a small negative $\xi_2$ while Models II–IV imply positive couplings that can lessen the coincidence problem and, depending on priors, may influence the inferred $H_0$ value. The results indicate Planck data are compatible with coupled dark energy models, though the ability to resolve the $H_0$ tension is model- and prior-dependent; time-invariant $ ext{ω}$ is a limitation and motivates future field-theoretic, time-dependent realizations. Overall, the work demonstrates that interacting dark sectors remain a viable extension to $ ext{Λ}$CDM in light of Planck, with implications for future cosmological modeling.

Abstract

Interacting Dark Energy and Dark Matter is used to go beyond the standard cosmology. We base our arguments on Planck data and conclude that an interaction is compatible with the observations and can provide a strong argument towards consistency of different values of cosmological parameters.

Figures (6)

• Figure 1: (Color online). Evolution of the dark energy/dark matter energy density ratio $r\equiv \rho_c/\rho_d$ in a model with $Q = 3H(\xi_1\rho_c + \xi_2\rho_d)$ for different coupling constants. (a) The red dashed line corresponds to Planck bestfit Model I, with $\xi_2 = -0.1881$ corresponding to the lowest value in the 68% C.L. as in Table \ref{['bestfit1']}. The black solid line has the same parameters but no interaction. (b) The black solid line corresponds to a non-interacting model with $w=-1.65$ and $\Omega_d=0.78$. The red dot-dashed line describes Model II listed in the first column of Table \ref{['bestfit2']} with $\xi_2=0.2$. The green dashed line corresponds to Planck bestfit Model III (see Table \ref{['bestfit3']}); and blue dotted line to Planck bestfit Model IV (see Table \ref{['bestfit4']}).
• Figure 2: (Color online). The likelihood of cold dark matter abundance $\Omega_c h^2$, dark energy EoS $\omega$ and couplings $\xi$ for the four models.
• Figure 3: (Color online). 2-D distribution for selected parameters - Model I.
• Figure 4: (Color online). 2-D distribution for selected parameters - Model II.
• Figure 5: (Color online). 2-D distribution for selected parameters - Model III.