## Abstract

We classify all minimal N-generational SU(3) × SU(2) × U(1) axion models according to the structure of their vacuum manifold M, showing that n ≡ π_{0}(M) is such that 1 ≤ n ≤ N. For n < N, the purely axial U(1)_{A} must be explicitly broken in the Yukawa sector, implying that U(1)_{PQ} necessarily distinguishes some quark families. In fact, a complete distinction, i.e. a fully horizontal realization of U(1)_{PQ} does exist for arbitrary N, leading to definite flavor interaction patterns with non-trivial relative structure of the mass matrices M_{u} versus M_{d}. For each n, in particular for the domain-wall-free n = 1 case, we find a unique Yukawa pattern embeddable in unified SU(5), whereas SO(10) can only host n = N. It is emphasized that axion invisibility guarantees the invisibility of flavor changing neutral currents.

Original language | English |
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Pages (from-to) | 647-670 |

Number of pages | 24 |

Journal | Nuclear Physics B |

Volume | 248 |

Issue number | 3 |

DOIs | |

State | Published - 31 Dec 1984 |

## ASJC Scopus subject areas

- Nuclear and High Energy Physics