1202.0005 (Shahab Joudaki)
Shahab Joudaki
From a combination of probes including the cosmic microwave background
(WMAP7+SPT), Hubble constant (HST), baryon acoustic oscillations (SDSS+2dFGRS),
and supernova distances (Union2), we have explored the extent to which the
constraints on the effective number of neutrinos and sum of neutrino masses are
affected by our ignorance of other cosmological parameters, including the
curvature of the universe, running of the spectral index, primordial helium
abundance, evolving late-time dark energy, and early dark energy. In a combined
analysis of the effective number of neutrinos and sum of neutrino masses, we
find mild (2.2 sigma) preference for additional light degrees of freedom.
However, the effective number of neutrinos is consistent with the canonical
expectation of 3 massive neutrinos and no extra relativistic species to within
1 sigma when allowing for evolving dark energy and relaxing the strong
inflation prior on the curvature and running. The agreement improves with the
possibility of an early dark energy component, itself constrained to be less
than 5% of the critical density (95% CL) in our expanded parameter space. In
extensions of the standard cosmological model, the derived amplitude of linear
matter fluctuations sigma_8 is found to closely agree with low-redshift cluster
abundance measurements. The sum of neutrino masses is robust to assumptions of
the effective number of neutrinos, late-time dark energy, curvature, and
running at the level of 1.2 eV (95% CL). The upper bound degrades to 2.0 eV
(95% CL) when further including the early dark energy density and primordial
helium abundance as additional free parameters. Even in extended cosmological
parameter spaces, Planck alone could determine the possible existence of extra
relativistic species at 4 sigma confidence and constrain the sum of neutrino
masses to 0.2 eV (68% CL).
View original:
http://arxiv.org/abs/1202.0005
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