ИСТИНА

The NSVZ $\beta$-function can be naturally obtained in $N=1$ supersymmetric electrodynamics (SQED) in terms of the bare coupling constant, if the theory is regularized by higher derivatives. However, if the renormgroup functions are defined in terms of the renomalized coupling constant, it is necessary to specify a subtraction scheme in which the NSVZ relation between the $\beta$-function and the anomalous dimension is valid. We show that such a scheme can be constructed by imposing simple boundary conditions to the renormalization constants. The NSVZ scheme constructed by this way is equivalent to application of the MOM-subtractions prescription supplemented by the additional finite renormalization, which is fixed by these conditions. Using results of explicit calculations at the three-loop level, we demonstrate how to relate this scheme with the $\overline{DR}$-scheme.