I will discuss the high-energy limit of gauge-theory amplitudes focusing on their infrared factorization properties. Soft-collinear factorization and Regge factorization provide two complementary viewpoints on this limit, which can be usefully combined to provide new insights: for example, it has been shown in this way that the simplest form of Regge factorization fails starting at next-to-next-to-leading logarithmic accuracy. I will propose a framework to organize the calculation of parton amplitudes at leading power in $t/s$, in terms of factorizing and non-factorizing contributions. This leads to explicit expressions for the leading Reggeization-breaking terms in two-loop and three-loop quark and gluon amplitudes in QCD, and yields a set of interesting constraints on infrared-finite contributions to high-energy scattering.
The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..