Higher neutrino mass allowed if Cold Dark Matter and Dark Energy are coupled

TL;DR

Coupling between Cold Dark Matter and Dark Energy significantly relaxes cosmological neutrino mass limits, allowing higher masses and addressing the coincidence problem, as shown through Fisher-matrix analysis.

Contribution

This paper demonstrates that coupling between CDM and DE can double neutrino mass limits and provides a quantitative analysis using Fisher-matrix techniques.

Findings

Neutrino mass limits are increased by more than a factor of 2 with CDM-DE coupling.

Coupling levels of β ≈ 0.15 are compatible with higher neutrino masses.

Coupling displaces $P(k)$ and $C_l$ spectra in opposite directions to neutrino mass effects.

Abstract

Cosmological limits on neutrino masses are softened, by more than a factor 2, if Cold Dark Matter (CDM) and Dark Energy (DE) are coupled. In turn, a neutrino mass yielding $\Omega_\nu$ up to $\sim0.20$ allows coupling levels $\beta \simeq 0.15, $ or more, already easing the coincidence problem. The coupling, in fact, displaces both $P(k)$ and $C_l$ spectra in a fashion opposite to neutrino mass. Estimates are obtained through a Fisher--matrix technique.