N = 1 supersymmetry and the three-loop gauge β-function

We calculate the three-loop gauge β-function for an abelian N = 1 supersymmetric gauge theory, using DRED. We construct a coupling constant redefinition that relates the result to the corresponding term in the NSVZ β-function, and by generalising this redefinition to the non-abelian case we derive the DRED three-loop gauge β-function for the non-abelian case.