A grand unified supersymmetric theory of flavor

A grand unified SU(5) theory is constructed with a hierarchical breaking of a U(2) flavor symmetry. The small parameters of the squark and slepton mass matrices, necessary to solve the supersymmetric flavor-changing problem, and the intergenerational quark and lepton mass hierarchies are both generated from the U(2) symmetry breaking parameters. The flavor interactions of the theory are tightly constrained, with just 10 free Peal parameters for both the fermion and scalar sectors. All but one of the 8 small fermion mass ratios, and all of the 3 small Cabibbo-Kobayashi-Maskawa mixing angles, can be understood without introducing small dimensionless Yukama parameters. Predictions are made for 2 of the Cabibbo-Kobayashi-Maskawa a mixing angles and for 2 of the fermion masses. The six flavor mixing matrices which appeal at the neutralino vel tices, and which in general are arbitrary unitary matrices, are determined in terms of just a single free parameter.