Are priors responsible for cosmology favoring additional neutrino species?

TL;DR

This paper reevaluates cosmological data to determine if priors influence the evidence for extra neutrino species, finding no support for deviations from the standard three neutrinos once prior effects are minimized.

Contribution

It introduces a prior-independent analysis of cosmological data, clarifying the evidence for additional neutrino species.

Findings

No evidence for extra neutrino species after prior-independent analysis

Cosmological data do not favor additional forms of radiation beyond standard neutrinos

Prior dependence affects the interpretation of neutrino count evidence

Abstract

It has been suggested that both recent cosmological data and the results of flavor oscillation experiments (MiniBooNE and LSND) lend support to the existence of low-mass sterile neutrinos. The cosmological data appear to weakly favor additional forms of radiation in the Universe, beyond photons and three standard neutrino families. We reconsider the cosmological evidence by making the resulting confidence intervals on the additional effective neutrino species as prior-independent as possible. We find that, once the prior-dependence is removed, the latest cosmological data show no evidence for deviations from the standard number of neutrino species.