Soft and Collinear Gluons in Perturbative QCD

ABSTRACT:
I will give a general introduction to the problem of infrared and collinear singularities in perturbative QCD, explaining our current understanding and pointing to several applications. Specifically, I will discuss how singularities arise in Feynman diagram calculations, and how they are bypassed to build meaningful physical observables; I will introduce some of the technology needed to prove factorization theorems and to derive Sudakov resummations for physically interesting cross sections; I will describe some recent developments concerning the structure of singularities for general QCD amplitudes to all orders in perturbation theory.