I am reading Akhmedovs 2000 paper on parametric resonance, and I cannot figure out the math of this particular passage:
The difference of the neutrino eigenenergies in a matter of density $N_i$ is $2\omega_i$, so that the oscillations phases aquired over the intervals $T_1$ and $T_2$ are
$2\phi_1=2\omega_1T_1$, $2\phi_2=2\omega_2T_2$
My question here is: What is the relevant formula that links eigenenergy to phase? And angular velocity to eigenenergy?