  The Flavour Symmetry of the Standard Model (SM) gauge sector is broken by the
fermion Yukawa couplings. Promoting the Yukawa matrices to scalar spurion
fields, one can break the flavour symmetry spontaneously by giving appropriate
vacuum expectation values (VEVs) to the spurion fields, and one encounters
Goldstone modes for every broken flavour symmetry generator. In this paper, we
point out various aspects related to the possible dynamical interpretation of
the Goldstone bosons: (i) In an effective-theory framework with local flavour
symmetry, the Goldstone fields represent the longitudinal modes for massive
gauge bosons. The spectrum of the latter follows the sequence of
flavour-symmetry breaking related to the hierarchies in Yukawa couplings and
flavour mixing angles. (ii) Gauge anomalies can be consistently treated by
adding higher-dimensional operators. (iii) Leaving the U(1) factors of the
flavour symmetry group as global symmetries, the respective Goldstone modes
behave as axions which can be used to resolve the strong CP problem by a
modified Peccei-Quinn mechanism. (iv) The dynamical picture of flavour symmetry
breaking implies new sources of flavour-changing neutral currents, which arise
from integrating out heavy scalar spurion fields and heavy gauge bosons. The
coefficients of the effective operators follow the minimal-flavour violation
principle.
