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MSbar-like schemes in QCD have in general the running coupling which containsLandau singularities, i.e., singularities outside the timelike semi-axis, atlow squared momenta. As a consequence, evaluation of the spacelike quantities,such as current correlators, in terms of (powers of) such a coupling thenresults in quantities which contradict the basic principles of Quantum FieldTheories. On the other hand, in those QCD frameworks where the running couplingremains finite at low squared momenta (IR freezing), the coupling usually doesnot have Landau singularities in the complex plane of the squared momenta. Iargue that in such QCD frameworks the spacelike quantities should not beevaluated as a power series, but rather as a series in derivatives of thecoupling with respect to the logarithm of the squared momenta. Such series showconsiderably better convergence properties. Moreover, Pade-related resummationsof such logarithmic derivative series give convergent series, thus eliminatingthe practical problem of series divergence due to renormalons.

Evaluations of low-energy physical quantities in QCD with IR freezing of the coupling