ULTRAVIOLET-RENORMALON CALCULUS

We consider the status of the so-called ultraviolet (UV) renormalon wh ich contributes to large order divergences of perturbative expansions in quantum chromodynamics. We argue that although the renormalon is as sociated with short distance dynamics, the class of renormalon graphs is not well defined and its overall weight is not controlled by theory . From this point of view there is not much difference from the case o f Borel nonsummable singularities. Phenomenologically the UV renormalo n is related to an effective four-fermion interaction originating with in fundamental QCD.