Hierarchical structure of physical Yukawa couplings from matter field K\"ahler metric

TL;DR

This paper explores how the matter field K"ahler metric influences the hierarchy of physical Yukawa couplings in string compactifications, revealing new mechanisms for generating realistic fermion mass structures.

Contribution

It demonstrates that kinetic mixing from the K"ahler metric can produce hierarchical Yukawa couplings even with trivial holomorphic couplings, using heterotic string models.

Findings

Hierarchical Yukawa couplings arise from kinetic mixing effects.

Pure untwisted modes on toroidal orbifolds exhibit hierarchical couplings.

Hierarchical couplings also found among untwisted and twisted modes on resolved orbifolds.

Abstract

We study the impacts of matter field K\"ahler metric on physical Yukawa couplings in string compactifications. Since the K\"ahler metric is non-trivial in general, the kinetic mixing of matter fields opens a new avenue for realizing a hierarchical structure of physical Yukawa couplings, even when holomorphic Yukawa couplings have the trivial structure. The hierarchical Yukawa couplings are demonstrated by couplings of pure untwisted modes on toroidal orbifolds and their resolutions in the context of heterotic string theory with standard embedding. Also, we study the hierarchical couplings among untwisted and twisted modes on resolved orbifolds.