Distinguishing interacting dark energy from wCDM with CMB, lensing, and baryon acoustic oscillation data

TL;DR

This study uses Planck CMB, lensing, and BAO data to constrain models where dark matter and dark energy interact, finding that non-phantom models show no significant interaction, while phantom models favor energy transfer from dark energy to dark matter.

Contribution

It provides new constraints on dark matter-dark energy interaction rates using combined CMB, lensing, and BAO data, especially distinguishing between phantom and non-phantom dark energy models.

Findings

Non-phantom models show no significant interaction, consistent with zero.

Phantom models favor energy transfer from dark energy to dark matter.

Lensing data slightly shifts interaction constraints in phantom models.

Abstract

We employ the Planck 2013 CMB temperature anisotropy and lensing data, and baryon acoustic oscillation (BAO) data to constrain a phenomenological $w$CDM model, where dark matter and dark energy interact. We assume time-dependent equation of state parameter for dark energy, and treat dark matter and dark energy as fluids whose energy-exchange rate is proportional to the dark-matter density. The CMB data alone leave a strong degeneracy between the interaction rate and the physical CDM density parameter today, $\omega_c$, allowing a large interaction rate $|\Gamma| \sim H_0$. However, as has been known for a while, the BAO data break this degeneracy. Moreover, we exploit the CMB lensing potential likelihood, which probes the matter perturbations at redshift $z \sim 2$ and is very sensitive to the growth of structure, and hence one of the tools for discerning between the $\Lambda$CDM model and its alternatives. However, we find that in the non-phantom models ($w_{\mathrm{de}}>-1$), the constraints remain unchanged by the inclusion of the lensing data and consistent with zero interaction, $-0.14 < \Gamma/H_0 < 0.02$ at 95\% CL. On the contrary, in the phantom models ($w_{\mathrm{de}}<-1$), energy transfer from dark energy to dark matter is moderately favoured over the non-interacting model; $-0.57 < \Gamma/H_0 < -0.10$ at 95\% CL with CMB+BAO, while addition of the lensing data shifts this to $-0.46 < \Gamma/H_0 < -0.01$.