Lepton masses and mixing from modular S4 symmetry

We study models of lepton masses and mixing based on broken modular invariance. We consider invariance under the finite modular group Gamma(4) similar or equal to S-4 and focus on the minimal scenario where the expectation value of the modulus is the only source of symmetry breaking, such that no flavons need to be introduced. After constructing a basis for the lowest weight modular forms, we build two minimal models, one of which successfully accommodates charged lepton masses and neutrino oscillation data, while predicting the values of the Dirac and Majorana CPV phases. (C) 2018 The Authors. Published by Elsevier B.V.