Abstract
Renormalization-group equations for the QCD coupling constant alpha-bar(t) and running gauge parameter a(t) in the two-loop approximation are discussed. It is pointed out that in momentum subtraction schemes the evolution of alpha-bar(t) may be different than in the minimal subtraction scheme because of the dependence of ..beta../sub 2/ on the gauge parameter. In the concrete case of the asymmmetric momentum subtraction scheme it is found that, for the negative initial gauge parameters, alpha-bar(t) does not tend to zero for t..-->..infinity. This indicates that the ultraviolet behavior of alpha-bar(t) may strongly depend on the renormalization scheme and on the gauge parameter.
Published Version
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