A new theoretical insight into the pattern of neutrino mixing and leptonic $CP$ violation is presented. It leads naturally and uniquely to a specific dark sector of three real neutral scalar singlets, with the radiative implementation of the inverse seesaw mechanism for neutrino mass. The new simple but crucial enabling idea is that a familiar $A_4$ transformation turns any orthogonal $3 \times 3$ matrix into one which predicts $\theta_{ 23} = \pi/4$ and $\delta_{ CP} = \pm \pi/2$ for the neutrino mixing matrix, in good agreement with present data.
Categories: hep-ph