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Isn't mass a fixed and an intrinsic property of a particle? How can we talk about eigenstates of the mass in the context of neutrinos?

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marked as duplicate by DavePhD, Brandon Enright, John Rennie, Qmechanic May 8 at 10:52

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Mass is not fixed... considering accelerators and E=mc^2. Energy is an eigenvalue, so the same applies to mass. –  somewherehere May 2 at 21:45
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Related: physics.stackexchange.com/q/91498 –  Alfred Centauri May 2 at 22:31
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@cppinitiator The "mass of a particle" means (in modern parlance) the Lorentz invariant mass (you may know it as the "rest mass"). There is nothing wrong with the idea of relativistic mass as such, but significant parts of physics have deprecated the term. Particle physics is one of those areas. –  dmckee May 3 at 0:51