# Time evolution using the Dirac equation

In non-relativistic qantum mechanics, the energy eigenstates (i.e.e eigensattes of the hamiltonian) evolve in phase according to their eigenenergies

$$\phi_(t) = e^{-iE_nt}\phi_n(0)$$

using natural units.

I am taking a course in particle physics, and there was a section on neutrino oscillations. In the caluclation of the probability of finding a neutrino in a diffrent state, the neutrino mass eigensates were assumed to evolve as above. However we are working with realtivitstic quantum mechnaics now. It is not clear to me why the states evolve in the same way.