Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Massive sterile neutrinos as warm Dark Matter

A. D. Dolgov, S. H. Hansen

TL;DR

This paper investigates whether massive sterile neutrinos can constitute warm dark matter by solving the early-universe production problem with a momentum-dependent Boltzmann equation that includes matter suppression of the mixing angle. It derives a relic-abundance condition that yields a mass–mixing relation, identifying a viable window with $m_s\lesssim 40\,{\rm keV}$ (lower for ν_e) and $\sin^2 2\theta \gtrsim 10^{-11}$. It then applies decay and gamma-ray bounds from radiative decays and SN1987A, showing that keV-scale sterile neutrinos can be consistent with observations while remaining testable via structure formation and diffuse-background measurements. The work positions keV sterile neutrinos as a natural warm dark matter candidate with concrete cosmological and astrophysical signatures.

Abstract

We show that massive sterile neutrinos mixed with the ordinary ones may be produced in the early universe in the right amount to be natural warm dark matter particles. Their mass should be below 40 keV and the corresponding mixing angles sin^2 2θ> 10^{-11} for mixing with ν_μor ν_τ, while mixing with ν_e is slightly stronger bounded with mass less than 30 keV.

Massive sterile neutrinos as warm Dark Matter

TL;DR

This paper investigates whether massive sterile neutrinos can constitute warm dark matter by solving the early-universe production problem with a momentum-dependent Boltzmann equation that includes matter suppression of the mixing angle. It derives a relic-abundance condition that yields a mass–mixing relation, identifying a viable window with (lower for ν_e) and . It then applies decay and gamma-ray bounds from radiative decays and SN1987A, showing that keV-scale sterile neutrinos can be consistent with observations while remaining testable via structure formation and diffuse-background measurements. The work positions keV sterile neutrinos as a natural warm dark matter candidate with concrete cosmological and astrophysical signatures.

Abstract

We show that massive sterile neutrinos mixed with the ordinary ones may be produced in the early universe in the right amount to be natural warm dark matter particles. Their mass should be below 40 keV and the corresponding mixing angles sin^2 2θ> 10^{-11} for mixing with ν_μor ν_τ, while mixing with ν_e is slightly stronger bounded with mass less than 30 keV.

Paper Structure

This paper contains 5 sections, 24 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Production of $\nu_s$ in the early universe
  3. Decay
  4. Discussion and conclusion
  5. Solving the Boltzmann equation

Figures (1)

  • Figure 1: Bounds from $(\nu_\alpha - \nu_s)$-mixing. The middle full line describes the mass-mixing relationship if sterile neutrinos are the dark matter for $(\nu_\tau - \nu_s)$-mixing. The two other full lines allow a factor 2 uncertainty in the amount of dark matter, $\Omega_{DM} = 0.15 -0.6$. The dashed line is for $(\nu_e - \nu_s)$-mixing. The hatched region for big masses is excluded by the Diffuse Gamma Background. The region above the dotted line is excluded by the duration of SN 1987A for $(\nu_\tau - \nu_s)$-mixing.