Neutrino Flavour Evolution Through Fluctuating Matter

TL;DR

This paper investigates how three-flavour neutrinos undergo flavor transformations in fluctuating matter, revealing new effects like induced transparency and turbulence response, with analytical solutions matching numerical results within a few percent.

Contribution

It introduces novel phenomena in neutrino flavor evolution due to multiple Fourier modes, extending understanding beyond two-flavour models and providing analytical solutions for complex turbulent scenarios.

Findings

Discovery of induced transparency effect in neutrino flavor transitions

Third Fourier mode can control transition probabilities, inducing transparency or opacity

Analytical solutions closely match numerical simulations within a few percent

Abstract

A neutrino propagating through fluctuating matter can experience large amplitude transitions between its states. Such transitions occur in supernovae and compact object mergers due to turbulent matter profiles and neutrino self-interactions. In this paper we study, both numerically and analytically, three-flavour neutrino transformation through fluctuating matter built from two and three Fourier modes. We find flavor transformation effects which cannot occur with just two flavours. For the case of two Fourier modes we observe the equivalent of "induced transparency" from quantum optics whereby transitions between a given pair of states are suppressed due to the presence of a resonant mode between another pair. When we add a third Fourier mode we find a new effect whereby the third mode can manipulate the transition probabilities of the two mode case so as to force complete transparency or, alternatively, restore "opacity" meaning the perturbative Hamiltonian regains its ability to induce neutrino flavour transitions. In both applications we find analytic solutions are able to match the amplitude and wavenumber of the numerical results to within a few percent. We then consider a case of turbulence and show how the theory can be used to understand the very different response of a neutrino to what appears to be two, almost identical, instances of turbulence.