We update a previous search for anisotropies in the neutrino background using the new results from the WMAP satellite. We found that the new data confirm the indication for anisotropies in the neutrino background at about similar to 2 sigma c.l.. Parametrizing the neutrino background through the viscosity parameter c(vis)(2), we demonstrate that current cosmological data provide the constraint c(vis)(2)> 0.145 at 95% c.l. We discuss the stability of the result when the assumptions of massless neutrinos and the number of massless neutrino families are relaxed. In particular, we found that an extra background of relativistic particles, still compatible with the data, prefers anisotropic stresses with c(vis)(2)> 0.09 at 95% c.l..
Anisotropies in the neutrino background: An update / Melchiorri, Alessandro; Paolo, Serra. - In: PHYSICAL REVIEW D, PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY. - ISSN 1550-7998. - 74:12(2006), pp. 127301-127307. [10.1103/physrevd.74.127301]
Anisotropies in the neutrino background: An update
MELCHIORRI, Alessandro;
2006
Abstract
We update a previous search for anisotropies in the neutrino background using the new results from the WMAP satellite. We found that the new data confirm the indication for anisotropies in the neutrino background at about similar to 2 sigma c.l.. Parametrizing the neutrino background through the viscosity parameter c(vis)(2), we demonstrate that current cosmological data provide the constraint c(vis)(2)> 0.145 at 95% c.l. We discuss the stability of the result when the assumptions of massless neutrinos and the number of massless neutrino families are relaxed. In particular, we found that an extra background of relativistic particles, still compatible with the data, prefers anisotropic stresses with c(vis)(2)> 0.09 at 95% c.l..I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
