Flavor instabilities in the neutrino line model

Abstract

A dense neutrino medium can experience collective flavor oscillations through nonlinear neutrino-neutrino refraction. To make this multi-dimensional flavor transport problem more tractable, all existing studies have assumed certain symmetries (e.g., the spatial homogeneity and directional isotropy in the early universe) to reduce the dimensionality of the problem. In this work we show that, if both the directional and spatial symmetries are not enforced in the neutrino line model, collective oscillations can develop in the physical regimes where the symmetry-preserving oscillation modes are stable. Our results suggest that collective neutrino oscillations in real astrophysical environments (such as core-collapse supernovae and black-hole accretion discs) can be qualitatively different from the predictions based on existing models in which spatial and directional symmetries are artificially imposed.Comment: 5 pages, 1 figur

Symmetric and standard matter neutrino resonances above merging compact objects

“…For example, for the case of core collapse supernovae neutrinos, it has been pointed out that several types of transformations can occur in such systems which have a slight electron neutrino excess, start at high neutrino density and end at low neutrino density; for recent work see e.g. [20][21][22][23][24][25][26][27]. At very high densities of neutrinos, more than one type of synchronized neutrino oscillation can occur, e.g.…”

Flavor instabilities in the multiangle neutrino line model

“…5. From this figure one can see that, unlike the two-beam Line model [15], the flavor instabilities in the multi-angle model depends on the neutrino mass hierarchy, and collective oscillations can begin at larger neutrino density in NH than in IH. One also sees that both µ …”

“…This study is a generalization of the work done for the two-beam Line model in Ref. [15] where only two neutrino beams are emitted from each neutrino source point. …”

“…It was also shown that the axial symmetry around the radial direction in the Bulb model can be broken spontaneously during collective neutrino oscillations [12,13]. Some very recent work has shown that the spatial symmetries in the low-dimensional models such as the spherical symmetry in the Bulb model can be broken in multi-dimensional models [14][15][16][17][18].…”

Supernova Neutrinos: New Challenges and Future Directions

“…However, more recently, it has been pointed out as new instabilities in the flavor space may arise by releasing such approximations. For example, within a simplified setup, it has been shown as breaking the axial symmetry [24], the spatial and directional symmetry [25], or by introducing temporal instabilities [26], flavor conversions could be induced (i.e., flavor instabilities can be determined because of the non-homogeneous or non-stationary conditions occurring within the stellar envelope). The same should be expected by considering a neutrino angular distribution not limited to the outward direction, as well as in the presence of large 3D effects that make the system inhomogeneous, non-stationary and anisotropic [15,16].…”