Coupling between cold dark matter and dark energy from neutrino mass experiments

TL;DR

This paper examines cosmologies where dynamical dark energy is linearly coupled to cold dark matter in the presence of massive neutrinos. Using MCMC analyses with CAMB/CosmoMC across RP and SUGRA potentials, it demonstrates a strong $β$–$M_ν$ degeneracy that is broken by external neutrino-mass priors, with BAO data slightly sharpening the preference for coupling. Incorporating KKDC priors yields a very high-significance detection of a nonzero coupling ($eta$), while prospective KATRIN priors remain substantially supportive of coupling as well; in contrast, phantom $w<-1$ scenarios do not mimic this feature effectively. The results imply that terrestrial neutrino measurements could reveal dark-sector interactions and that Planck data will further constrain these couplings, potentially falsifying $\\Lambda$CDM if a neutrino mass around $0.3$ eV is confirmed. This work highlights the dark sector as an avenue for integrating laboratory and cosmological observations.

Abstract

We consider cosmological models with dynamical dark energy (dDE) coupled to cold dark matter (CDM), while simultaneously allowing neutrinos to be massive. Using a MCMC approach, we compare these models with a wide range of cosmological data sets. We find a strong correlation between this coupling strength and the neutrino mass. This correlation persists when BAO data are included in the analysis. We add then priors on $ν$ mass from particle experiments. The claimed detection of $ν$ mass from the Heidelberg-Moscow neutrinoless double--$β$ decay experiment would imply a 7--$8 σ$ detection of CDM-DE coupling. Similarly, the detection of $ν$ mass from coming KATRIN tritium $β$ decay experiment will imply a safe detection of a coupling in the dark sector. Previous attempts to accommodate cosmic phenomenology with such possible $ν$ mass data made recourse to a $w < -1$ eoS. We compare such an option with the coupling option and find that the latter allows a drastic improvement.

Figures (4)

• Figure 1: 68% and 95% confidence intervals in the $M_\nu-\beta$ plane. The left panel shows resulting limits when using a SUGRA potential, while the right panel shows the limits when using a RP potential. Black, thin lines indicate the results when using WMAP5 as the only cosmological data set, and red, thick lines show the results when using WMAP5++. Dotted lines are the cosmology only limits. The resulting limits when also including the KKDC limit on $M_\nu$ are shown with solid lines. We notice that the intersection between $\beta$ and $M_\nu$ allowed areas, when KKDC controversial results are allowed or omitted, does not vanish but is rather small.
• Figure 2: 1D likelihood distributions for $\beta$, using WMAP5++ sets and the KKDC prior on $M_\nu$. Thick, red lines corresponds to the SUGRA model, while thin black lines refers to the the RP model. Solid lines denote marginalized likelihood. Dotted lines indicate average likelihood of the samples in each bin.
• Figure 3: The same as Figure \ref{['fig:KKDC']}, but using a KATRIN prior with a fiducial neutrino mass of $m_\beta = 0.3$eV ($M_{\nu} = 0.9$eV) instead of the KKDC prior. Let us also point out that, at variance from the KKDC case, the KATRIN prior is fully consistent with cosmological constraints, essentially leading to a restriction of the allowed area in the $M_\nu$--$\beta$ plane.
• Figure 4: Likelihood distribution with or without the KKDC prior (solid or dotted lines, respectively, indicating 1 and 2 $\sigma$'s), when a DE state parameter $w < -1$ is allowed and considering all cosmological data. Notice that the high likelihood areas, with or without the KKDC prior, have just a minor intersection at the 2--$\sigma$ level. Let us recall that, with the coupling option, there is a (small) intersection even at 1--$\sigma$.