Lower Bounds on U_{e3}

Understand

We give minimal values for the smallest lepton mixing parameter U_{e3}, applying 2-loop renormalization group equations in an effective theory approach.

• This is relevant in scenarios that predict an inverted neutrino mass spectrum with the smallest mass and U_{e3} being zero at tree level, a situation known to be preserved at 1-loop order.
• At 2-loop, U_{e3} is generated at a level of 10^{-12}-10^{-14}.
• Such small values are of interest in supernova physics.