Residual flavor symmetry breaking in the landscape of modular flavor models

TL;DR

This paper explores how small deviations from fixed points in the moduli space of string theory can explain fermion mass hierarchies and CP violation, with a focus on statistical preferences and phenomenological implications.

Contribution

It demonstrates that the string landscape favors tiny deviations from fixed points and analyzes the resulting effects on flavor models, especially in the lepton sector.

Findings

String landscape prefers deviations of order 10^{-5} from fixed points.

CP-breaking vacuum is statistically favored.

Distribution of moduli values impacts flavor phenomenology.

Abstract

We study a symmetry breaking of residual flavor symmetries realized at fixed points of the moduli space. In the supersymmetric modular invariant theories, a small departure of the modulus from fixed points is required to realize fermion mass hierarchies and sizable CP-breaking effects. We investigate whether one can dynamically fix the moduli values in the vicinity of the fixed points in the context of Type IIB string theory. It is found that the string landscape prefers $|\delta \tau| \simeq 10^{-5}$ for the deviation of the complex structure modulus from all fixed points and the CP-breaking vacuum is statistically favored. To illustrate phenomenological implications of distributions of moduli values around fixed points, we analyze the lepton sector on a concrete $A_4$ modular flavor model.