# Fully constrained mass matrix: Can symmetries alone determine the flavon vacuum alignments?

## TL;DR

This paper demonstrates that the vacuum alignments of flavons in a flavor symmetry model can be fully determined by residual symmetries of combined groups, leading to a unique, symmetry-driven construction of mass matrices.

## Contribution

It introduces a formalism where the flavor symmetry is a direct product of residual and extra groups, enabling complete determination of flavon vacuum alignments through residual symmetries.

## Key findings

- Vacuum alignments are eigenstates of residual symmetry elements.
- Coupling flavons results in a fully constrained sextet of 23.
- The formalism allows systematic construction of flavor models with symmetry-determined alignments.

## Abstract

In the framework of the representation theory of finite groups, it was recently shown that a fully constrained complex-symmetric mass matrix can be conveniently mapped into a sextet of $\Sigma(72\times3)$. In this paper, we introduce an additional flavor group $X_{24}$ in the model so that the vacuum alignment of the $\Sigma(72\times3)$ sextet is determined not only by the symmetries of $\Sigma(72\times3)$ but also by that of $X_{24}$. We define several flavons which transform as multiplets under $\Sigma(72\times3)$ as well as $X_{24}$. The vacuum alignment of each of these flavons is obtained as a simultaneous invariant eigenstate of specific elements of the groups $\Sigma(72\times3)$ and $X_{24}$; i.e.,~the vacuum alignment is fully determined by its residual symmetries. These flavons couple together uniquely resulting in the fully constrained sextet of $\Sigma(72\times3)$. Through this work we propose a general formalism in which the flavor symmetry group ($G_f$) is obtained as the direct product, $G_f=G_r \times G_x$. Fermions transform nontrivially only under $G_r$ while they remain invariant under $G_x$. Flavons, on the other hand, transform nontrivially under both $G_r$ and $G_x$. The vacuum alignment of each flavon multiplet transforming irreducibly under $G_r \times G_x$ is uniquely identified by its corresponding residual symmetry (a subgroup of $G_r \times G_x$). Several such flavons couple together to form an effective multiple of $G_r$ which remains invariant under $G_x$. This effective multiplet couples to the fermions.