1111.3810 (Eleonora Di Valentino et al.)

Future constraints on neutrino isocurvature perturbations in the curvaton scenario    [PDF]

Eleonora Di Valentino, Massimiliano Lattanzi, Gianpiero Mangano, Alessandro Melchiorri, Pasquale D. Serpico

In the curvaton scenario, residual isocurvature perturbations can be imprinted in the cosmic neutrino component after the decay of the curvaton field, implying in turn a non-zero chemical potential in the neutrino distribution. We study the constraints that future experiments like Planck or CMBPol will be able to put on the amplitude of isocurvature perturbations in the neutrino component. We express our results in terms of the square root gamma of the non-adiabaticity parameter alpha and of the extra relativistic degrees of freedom \Delta N_eff. Assuming a fiducial model with purely adiabatic fluctuations, we find that Planck (CMBPol) will be able to put the following upper limits at the 1sigma level: gamma < 5.3x10^{-3} (1.5x10^{-3}) and \Delta N_eff < 0.16\,(0.043). Finally, we recast these bounds in terms of the background neutrino degeneracy parameter xi and the corresponding perturbation amplitude sigma_xi, and compare with the bounds on xi that can be derived from Big Bang Nucleosynthesis

View original: http://arxiv.org/abs/1111.3810