ИСТИНА

We calculate terms quartic in the Yukawa couplings in the three-loop beta-function and in the two-loop anomalous dimension of the matter superfields for the N=1 supersymmetric Yang—Mills theory regularized by higher covariant derivatives. Comparing the results, we obtain that such contributions to the renormalization group functions defined in terms of the bare couplings satisfy the NSVZ relation independently of the subtraction scheme. This follows from the fact that the considered three-loop contribution to the beta-function is given by an integral of double total derivatives and can be reduced to the two-loop contribution to the anomalous dimension. For the simplest form of the higher derivative regularizing term we also calculate terms quartic in the Yukawa couplings in the renormalization group functions defined in terms of the renormalized couplings. These terms do not satisfy the NSVZ relation in the considered approximation for a general renormalization prescription. However, we demonstrate that in the case of using the recently proposed boundary conditions defining the NSVZ scheme in the non-Abelian case the NSVZ relation between the terms quartic in the Yukawa couplings is really valid.