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Most GUT models have some relationship between down-type quarks and leptons, that more or less agree with the observed values after running the renormalization equations. But, what about up-type quarks?

How good are GUT predictions for up-type quarks? And, particularly,

Is there some model explaining why the mass of charm is so near of the mass of the tau lepton?

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Accidental coincidence, if derived from GUT, is also a valid answer. –  arivero Nov 17 '11 at 11:46

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