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

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 ${\mathrm{\Omega }}_{\nu }$ up to $\sim 0.20$ 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.