Ultraviolet-renormalon calculus.
We consider the status of the so-called ultraviolet (UV) renormalon which contributes to large order divergences of perturbative expansions in quantum chromodynamics. We argue that although the renormalon is associated 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 of Borel nonsummable singularities. Phenomenologically the UV renormalon is related to an effective four-fermion interaction originating within fundamental QCD.