Quark mixings as a test of a new symmetry of quark Yukawa couplings

We assume that Yukawa couplings of up and down quarks are related by Yu∝Yd2 at grand unification (GU) scale. Using the specific ansatz for Yd we obtain the CKM matrix that is symmetrical at the GU scale and two relations between the quark masses. Using three specific models as illustrative examples for the evolution down to low energies, we obtain a non-symmetric CKM matrix whose entries are in good agreement with their measured values and two quark mass relations at the mt scale: (mu/mc)=(md/ms)2 and (mc/mt)=k(ms/mb)2 with the coefficient k fixed from the renormalization group (RG) evolution.