Derivation of the sterile neutrino Boltzmann equation from quantum kinetics

Abstract

An extensive, growing body of work has been penned on cosmologies that include one or more sterile neutrinos. Early entries in the literature formulated a Boltzmann-like equation describing sterile-neutrino production in a way that bypasses the numerical tracking of high-frequency complex phases, and meticulous quantum-kinetic analyses shortly thereafter put the formula on firmer ground. A new and more direct derivation is given here, showing that the equation follows almost immediately from a quantum relaxation-time approximation and an expansion in the mixing angle. Besides reproducing the desired result, the relaxation ansatz captures to a high degree of accuracy the interlaced dynamics of oscillations, decoherence, and plasma repopulation. Successes and limitations of the semiclassical equation are illustrated numerically and are shown to reflect the accuracy of the approximations employed in the derivation. The inclusion of interactions among the sterile neutrinos is also briefly addressed.

7 pages, 5 figures

References in corpus (5)

• Resonantly-Produced 7 keV Sterile Neutrino Dark Matter Models and the Properties of Milky Way Satellites
• Cosmology with self-interacting sterile neutrinos and dark matter - A pseudoscalar model
• Lepton Number-Driven Sterile Neutrino Production in the Early Universe
• Neutrino flavor transformation in the lepton-asymmetric universe
• Self-interacting sterile neutrino dark matter: the heavy-mediator case

Cited by in corpus (8)

• Collisional flavor instabilities of supernova neutrinos
• Self-consistency in models of neutrino scattering and fast flavor conversion
• Neutrino flavor mixing breaks isotropy in the early universe
• Subgrid modeling of neutrino oscillations in astrophysics
• The Hydrogen Mixing Portal, Its Origins, and Its Cosmological Effects
• Hydrogen Mixing as a Novel Mechanism for Colder Baryons in 21 cm Cosmology
• Opening up New Parameter Space for Sterile Neutrino Dark Matter
• Sterile neutrino production at small mixing in the early universe