Do many-particle neutrino interactions cause a novel coherent effect?

We investigate whether coherent flavor conversion of neutrinos in a neutrinobackground is substantially modified by many-body effects, with respect to theconventional one-particle effective description. We study the evolution of asystem of interacting neutrino plane waves in a box. Using its equivalence to asystem of spins, we determine the character of its behavior completelyanalytically. We find that, if the neutrinos are initially in flavoreigenstates, no coherent flavor conversion is realized, in agreement with theeffective one-particle description. This result does not depend on the size ofthe neutrino wavepackets and therefore has a general character. The validity ofthe several important applications of the one-particle formalism is thusconfirmed.Comment: 25 pages, 1 figur