Aaron Smith, Maria Archidiacono, Asantha Cooray, Francesco De Bernardis, Alessandro Melchiorri, Joseph Smidt
Recent cosmological data have provided new constraints on the number of
neutrino species and on the neutrino mass. However these constraints depend on
assumptions related to the underlying cosmology. Since a correlation is
expected between the number of effective neutrinos, N_{eff}, the neutrino mass
\sum M_\nu, and the curvature of the universe, \Omega_k, it is useful to
investigate the current constraints in the framework of a non-flat universe. In
this paper we update the constraints on neutrino parameters by making use of
the latest Cosmic Microwave Background (CMB) data from the ACT and SPT
experiments and consider the possibility of a universe with non-zero curvature.
We first find a negative correlation between curvature and N_{eff} with a
correlation coefficient of -0.36 and we place new constraints on N_{eff} and
\Omega_k, with N_{eff} = 4.03 +/- 0.45 and 10^3, \Omega_k = -4.46 +/- 5.24.
Thus, even when \Omega_k is allowed to vary, N_{eff} = 3 is still disfavored at
95% confidence. The correlation between neutrino mass and curvature is much
stronger, with a correlation coefficient of 0.78 that shifts the 95% upper
limit of \sum M_\nu < 0.446 eV to \sum M_\nu < 0.948 eV. Thus, the impact of
assuming flatness in neutrino cosmology is significant and an essential
consideration with future experiments.
View original:
http://arxiv.org/abs/1112.3006
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