Flavor Symmetry Breaking and Vacuum Alignment on Orbifolds

TL;DR

This paper introduces a novel framework for flavor symmetry breaking using boundary conditions in extra dimensions, enabling scalar vacuum alignment without detailed potential minimization, and applies it to lepton mass models with S3 and A4 symmetries.

Contribution

It proposes a new approach to flavor symmetry breaking via boundary conditions in extra dimensions, simplifying vacuum alignment and enabling realistic lepton mass models.

Findings

Scalar vacuum alignment achieved without potential minimization.

Models reproduce tri-bimaximal lepton mixing.

Broken S3 and A4 symmetries lead to realistic mass patterns.

Abstract

Flavor symmetry has been widely studied for figuring out the masses and mixing angles of standard-model fermions. In this paper we present a framework for handling flavor symmetry breaking where the symmetry breaking is triggered by boundary conditions of scalar fields in extra-dimensional space. The alignment of scalar expectation values is achieved without referring to any details of scalar potential and its minimization procedure. As applications to non-abelian discrete flavor symmetries, illustrative lepton mass models are constructed where the S3 and A4 flavor symmetries are broken down to the directions leading to the tri-bimaximal form of lepton mixing and realistic mass patterns.