Understand
By using most of the present CMB and LSS measurements and the BBN constraints on the primordial helium abundance, Y_p, we set bounds on the radiation content of the Universe and neutrino properties.
- We consider lepton asymmetric cosmological models parametrized by the neutrino degeneracy parameter \xi_{\nu} and the variation of the relativistic degrees of freedom, \Delta N_{oth}^{eff}, due to possible other physical processes that occurred between BBN and structure formation epoch.
- We found that present CMB and LSS data constraints the neutrino degeneracy parameter at \xi_{\nu} \leq 0.722, implying a lepton asymmetry of the neutrino background {\cal L}_{\nu} \leq 0.614 (2-\sigma).
- We also found \Delta N^{eff}_{oth}=0.572^{+1.972}_{-1.780}, the contribution to the effective number of relativistic neutrino species N^{eff}=3.058^{+1.971}_{-1.178} and a primordial helium abundance Y_p=0.249^{+0.014}_{-0.016} (2-\sigma errors).