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snorkack

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- There are two neutrino oscillation periods, each with a mass square difference, so at least two neutrino mass eigenstates of the three have nonzero masses. (Note that "imaginary" is also "nonzero"!)

- There is an upper bound on mass (below 100 meV) but there does not seem to be an observed lower bound on mass.

Is there any theoretical reason forbidding oscillations between an eigenstate of nonzero rest mass and an eigenstate of exactly zero rest mass?

The observed mass square differences are quoted as 76 and 2440 meV

^{2}. If the light eigenstate is, say, 2 meV, does it mean that the heavy eigenstates are 9 meV and 50 meV, or that they are 49 meV and 50 meV? Or that we do not know which?

How do oscillations work between mass eigenstates if the total energy is smaller than the mass of an eigenstate partaking in oscillation? Relic neutrinos should now be 0,5 meV if massless, less if massive. What did oscillations do on cooling?