We identify a generic new form of collective flavor oscillations in dense neutrino gases that amounts to a self-induced parametric resonance. It occurs in a homogeneous and isotropic ensemble when a range of neutrino modes is prepared in a different flavor than the neighboring modes with lower and higher energies. The flavor content of the intermediate spectral part librates relative to the other parts with a frequency corresponding to a typical $\Delta m^2/2E$. This libration persists in the limit of an arbitrarily large neutrino density where one would have expected synchronized flavor oscillations.

• Received 10 October 2008

DOI:https://doi.org/10.1103/PhysRevD.78.125015