Synchronisation and MSW sharpening of neutrinos propagating in a flavour   blind medium
  We consider neutrino oscillations in a medium in which scattering processes are blind to the neutrino flavour. We present an analytical derivation of the synchronised behaviour obtained in the limit where the average scattering rate is much larger than the oscillation frequency. We also examine MSW transitions in these circumstances, and show that a sharpening of the transition can result. 
Nicole F. Bell, R. F. Sawyer and Raymond R. Volkas