Unified models of neutrinos, flavour and CP Violation

Recent data from neutrino experiments gives intriguing hints about the mass ordering, the CP violating phase and non -maximal atmospheric mixing. There seems to be a (one sigma) preference for a normal ordered (NO) neutrino mass pattern, with a CP phase 8 = -100 degrees 50 degrees, and (more significantly) non -maximal atmospheric mixing. Global fits for the NO case yield lepton mixing angle one sigma ranges: theta(23) approximate to 41.4 degrees +/- 1.6 degrees, theta(12) approximate to 33.2 degrees 1.2 degrees, theta(13) approximate to 8.45 degrees +/- 0.15 degrees. Cosmology gives a limit on.the total of the three masses to be below about 0.23 eV, favouring hierarchical neutrino masses over quasi degenerate masses. Given such experimental advances, it seems an opporttne moment to review the theoretical status of attempts to explain such a pattern of neutrino masses and lepton mixing, focusing on approaches based on the four pillars of: predictiVity,minimality, robustness and unification. Predictivity can result from various mixing sum rules whose status is reviewed. Minimality can follow from the type I seesaw mechanism, including constrained sequential dominance of right-handed (RH) neutrinos, and the littlest seesaw model. Robustness requires enforcing a discrete CP and non -Abelian fainily symmetry, spontaneously broken by flavons with the symmetry preserved in a semi-direct way. Unification can account for all lepton and quark masses, mixing angles and CP phases, as in Supersymmetric Grand Unified Theories of Flavour, with possible string theory origin. (C) 2017 Elsevier B.V. All rights reserved.