Inflationary freedom and cosmological neutrino constraints

Abstract

The most stringent bounds on the absolute neutrino mass scale come from cosmological data. These bounds are made possible because massive relic neutrinos affect the expansion history of the universe and lead to a suppression of matter clustering on scales smaller than the associated free streaming length. However, the resulting effect on cosmological perturbations is relative to the primordial power spectrum of density perturbations from inflation, so freedom in the primordial power spectrum affects neutrino mass constraints. Using measurements of the cosmic microwave background (CMB), the galaxy power spectrum and the Hubble constant, we constrain neutrino mass and number of species for a modelindependent primordial power spectrum. Describing the primordial power spectrum by a 20-node spline, we find that the neutrino mass upper limit is a factor 3 weaker than when a power law form is imposed, if only CMB data are used. The primordial power spectrum itself is constrained to better than 10% in the wave vector range k ≈ 0.01 − 0.25 Mpc −1 . Galaxy clustering data and a determination of the Hubble constant play a key role in reining in the effects of inflationary freedom on neutrino constraints. The inclusion of both eliminates the inflationary freedom degradation of the neutrino mass bound, giving for the sum of neutrino masses Σm ν < 0.18 eV (at 95% confidence level, Planck þ BOSS þ H 0 ), approximately independent of the assumed primordial power spectrum model. When allowing for a free effective number of species, N eff , the joint constraints on Σm ν and N eff are loosened by a factor 1.7 when the power law form of the primordial power spectrum is abandoned in favor of the spline parametrization.

Features and new physical scales in primordial observables: Theory and observation

“…With present data, the constraints on the ΛCDM model's late-time cosmological parameters are in fact surprisingly stable when one allows a very general shape of the power spectrum compared to the power-law case [505,15] (though in extended models this statement may not hold [506]). …”

Relic neutrinos, thermal axions, and cosmology in early 2014

“…[8]. The addition of Baryon Acoustic Oscillation (BAO) measurements from the Sloan Digital Sky Survey (SDSS)-II Data Release 7 [20,21], from the WiggleZ survey [22], from the Baryon Acoustic Spectroscopic Survey (BOSS) [23], one of the four surveys of SDSS-III [24] Data Release 9 [25] and from 6dF [26] to Planck CMB measurements also significantly improves the neutrino mass constraints, leading to m ν < 0.26 eV at 95% CL (see also the recent work of [27]). …”

Dark radiation and inflationary freedom

“…[12,13,14,15]. These works show some common results: there is a range of wavemodes where the PPS is well in agreement with the PL form, but some deviations can exist below k 0.004 Mpc −1 .…”

“…In the range (log k 2 , log k 11 ) the nodes are equally spaced, since this is the wavemode range were the data constraints are stronger [13]. We fix the first and last nodes to ensure that all the evaluations of the PPS are inside the covered range: consequently, we expect that P s,1 and P s, 12 are less constrained by the data.…”