Self-induced conversion in dense neutrino gases: Pendulum in flavour space
By S. Hannestad, G. Raffelt, G. Sigl, Y. Wong. 2006
140 citations recorded by the source corpus.
Neutrino-neutrino interactions can lead to collective flavour conversion effects in supernovae and in the early universe. We demonstrate that the case of “bipolar” oscillations, where a dense gas of neutrinos and antineutrinos in equal numbers completely converts from one flavour to another even if the mixing angle is small, is equivalent to a pendulum in flavour space. Bipolar flavour conversion corresponds to the swinging of the pendulum, which begins in an unstable upright position (the initial flavour), and passes through momentarily the vertically downward position (the other flavour) in the course of its motion. The time scale to complete one cycle of oscillation depends logarithmically on the vacuum mixing angle. Likewise, the presence of an ordinary medium can be shown analytically to contribute to a logarithmic increase in the bipolar conversion period. We further find that a more complex (and realistic) system of unequal numbers of neutrinos and antineutrinos is analogous to a spinning top subject to a torque. This analogy easily explains how such a system can oscillate in both the bipolar and the synchronised mode, depending on the neutrino density and the size of the neutrino-antineutrino asymmetry. Our simple model applies strictly only to isotropic neutrino gasses. In more general cases, and especially for neutrinos streaming from a supernova core, different modes couple to each other with unequal strength, an effect that can lead to kinematical decoherence in flavour space rather than collective oscillations. The exact circumstances under which collective oscillations occur in non-isotropic media remain to be understood.
View Paper: https://www.semanticscholar.org/paper/087a981d26f35303d44da3a1756170138ae56a22
How researchers see this paper
The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.
Citations in the corpus
- Collective neutrino flavor transitions in supernovae and the role of trajectory averaging (2007, methodology): “(57)-(58) describe a gyroscopic pendulum in flavor space [41, 42].”
- Large underground, liquid based detectors for astro-particle physics in Europe: scientific case and prospects (2007, background): “As an important caveat, we mention that very recently it has been recognized that non-linear oscillation effects caused by neutrino–neutrino interactions can have a dramatic impact on the neutrino flavour evolution for approximately the first 100 km above the neutrino sphere [84, 85].”
- Self-induced spectral splits in supernova neutrino fluxes (2007, background): “From the dynamics of the flavor pendulum [11, 12] we know that in the end P̄ is antialigned with B, whereas P retains a large transverse component because Pz − P̄z is conserved: The system prepares itself for a spectral split.”
- Collective neutrino flavor conversion: Recent developments (2016, background): “The upper pair (symmetric solution) corresponds to the traditional flavor pendulum [10,11].”