Speaker
Gorazd Cvetic
Description
We present several schemes of QCD with running coupling with finite value in the infrared (IR). Such couplings, in comparison with usual perturbative couplings with Landau singularities, usually (but not always) contain nonperturbative contributions and, when combined with OPE, better describe IR sector. We then show that evaluation of spacelike renormalization group invariant QCD quantities, such as current correlators or structure functions, in the form of truncated power series of such IR finite couplings often leads to unphysical and highly divergent results. We show that, instead, truncated expansions in the logarithmic derivatives of the coupling are more stable and keep the nonperturbative contributions under control. Extension to evaluation of timelike quantities is explained. Programs in Mathematica and in Fortran for evaluations are presented.
Author
Gorazd Cvetic
