= Adiabatic matter-enhanced neutrino conversion
{title2=$P_{ee}=\sin^2\theta$}
Flavor conversion in a slowly varying medium when an occupied instantaneous propagation eigenstate follows its eigenvalue branch without transitions to the other branch. For positive electron-neutrino matter potential and normal two-state ordering, a high-density <electron neutrino> follows the upper branch into the vacuum <mass eigenstate> $\nu_2$. Detection in the electron flavor then has <probability> $\sin^2\theta$, rather than the phase-averaged vacuum value $1-\tfrac12\sin^22\theta$. High production density alone does not guarantee adiabatic evolution.
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