Modular symmetry anomaly and non-perturbative neutrino mass terms in magnetized orbifold models

Understand

We study the modular symmetry anomaly in magnetized orbifold models.

• The non-perturbative effects such as D-brane instanton effects can break tree-level symmetry.
• We study which part of the modular symmetry is broken explicitly by Majorana mass terms with three generations of neutrinos.
• The modular weight of neutrino mass terms does not match with other coupling terms in tree-level Lagrangian.