this range, $w_\nu$ is far from zero, especially for low masses. There is thus a degeneracy between the characteristic redshift of the sources and the neutrino mass, which is independent of the well-known redshift-mass degeneracy defined by the amplitude of the cosmic shear signal.

The total matter power spectrum in Eq. (\[eq:pgamma\]) is computed following Hannestad [et al. ]{}(2006), which is also similar to the description adopted for perturbed quintessence fields [@csquintessence]. By assuming that the neutrino overdensities remain always in the linear regime while CDM and baryons grow non-linearly, the total matter power spectrum is given by $$\label{eq:Pnl}
P_{\mathrm{m}}^{{\small\mathrm{nl}}}(k,z)=\left[ f_\nu
\sqrt{P_\nu^{{\small\mathrm{lin}}}(k,z)}+(f_{\mathrm{cdm}}+f_{\mathrm{b}})\sqrt{P_{{\mathrm{cdm}}+{\mathrm{b}}}^{{\small\mathrm{nl}}}(k,z)}\right]^2,$$ where $f_i\equiv\Omega_i/{\Omega_{\mathrm{m}}}$ with $i=\{\nu,{\mathrm{cdm}},{\mathrm{b}}\}$ are the density fractions of each matter field over the total matter density parameter ${\Omega_{\mathrm{m}}}={\Omega_\mathrm{cdm}}+{\Omega_\mathrm{b}}+{\Omega_\nu}$. The linear power spectra $P_i^{{\small\mathrm{lin}}}(k,z)$ are computed using the Boltzmann code CAMB [^2], to take into account properly the scale-dependent growth of the neutrino perturbations. The output is computed for a grid of redshifts linearly spanning the range $0<z\leq 4$ and then spline-interpolated. The non-linear spectrum $P_{{\mathrm{cdm}}+{\mathrm{b}}}^{{\small\mathrm{nl}}}$ is computed with the [halofit]{} mapping [@halofit]. The Peacock & Dodds mapping [@PD] is unsuitable for this study, because it uses a scale-independent growth factor, which cannot be defined in the presence 