The Local Potential Approximation (LPA) to the Wetterich-equation is formulated explicitly in terms of operators, which are invariant under the U(n)× U(n) symmetry group. Complete formulas are presented for the two-flavor (U(2)× U(2)) case. The same approach leads to a unique natural truncation of the functional driving the renormalisation flow of the potential of the three-flavor case (U(3)× U(3)). The procedure applied to the SU(3)× SU(3) symmetric theory, results in an equation, which

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... ally allows an RG-investigation of the effect of the 't Hooft term representing the U_A(1) anomaly, disentangled from the other operators.