Behavior of the Effective QCD Coupling in the Infrared Region

The summary of nonperturbative results for the QCD invariant coupling obtained by numerical lattice simulations for the path integral and by solution of the approximate Dyson–Schwinger equations reveals a remarkable variety of IR behaviors of even at the qualitative level. In turn, this raises the question of the correspondence between the results obtained by different groups. We analyze this issue in terms of mass-dependent coupling-constant transformations and conclude that the problem of the IR behavior of the effective QCD coupling and of propagators is not well defined and requires a further clarification.