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From Long to Short Distances in Perturbative QCD

Infrared safe differential cross sections, such as event shape distributions, can be measured over wide kinematic ranges, from regions where fixed order calculations are adequate to regions where nonperturbative dynamics dominate. Such observables provide an ideal laboratory for the study of the transition between weak and strong coupling in quantum field theory. This talk begins with some of the fundamentals of the perturbative description of QCD and the basis of resummation techniques, followed by a brief discussion of selected topics from recent fixed-order and resummed calculations. It focuses on how resummed perturbation theory has been used to deduce the structure of nonperturbative corrections, and to provide a framework with which to address the transition from short- to long-distance dynamics in QCD.