Symmetry of Lepton Mixing

Understand

Neutrino mixing is studied from a symmetry perspective, both bottom-up and top-down.

• In the bottom-up approach, we start from the tri-bimaximal mixing, or one of its three partial patterns, and construct a list of horizontal symmetry groups capable of reproducing the mixng without adjustment of parameters.
• This list, labeled by an integer $n\ge 3$, is explicitly calculated for $n=3$.
• In the top-down approach, we start from any finite group possessing a three-dimensional irreducible representation and an order-2 element, give a recipe to determine what mixing pattern it contains, and how to construct a dynamical model to reveal a particular mixing.