Year: 2026
Type: preprint
Abstract: We study the impact of flavour-specific neutrino self-interactions on the CMB anisotropy spectrum and consistently take into account neutrino mixing. Starting from the neutrino quantum kinetic equations, we derive the neutrino Boltzmann hierarchies for the neutrino mass states. Our work shows that most scenarios of flavour-specific neutrino self-interactions are well approximated by a combined fluid approach. In practice, this implies that existing CMB bounds on the effective neutrino coupling are weakened by a factor $\sqrt{2}$ for scenarios in which only two neutrino flavours interact (irrespective of which flavours). If only one neutrino flavour interacts the bounds are weaker by a factor $\sqrt{6}$, with the only caveat that the combined fluid approach is less reliable for only $ν_e$ interacting.
Source: arXiv (Cornell University)
Language: English
Topic: Neutrino Physics Research
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G103507813, G1105844351, G1175115578, G1272900390, G1550511538, G1880773934, G2188020438, G2262748287, G2917513873, G296130331, G300979063, G3345895242, G3480869486, G4090823411, G425668148, G464105488, SFB 1258: Neutrinos und Dunkle Materie in der Astro und Teilchenphysik (NDM), G491712853, G5017550144, G5080475149, G5209569390, G5635532810, G6281504974, G6466192506, G7084143925, G714608666, G7169023097, G7805626310, G7863371703, G7984235579, G8497050386, G8800515849
OpenAlex ID: W7213270624