Description
In the high-energy or Regge limit, gauge-theory scattering amplitudes can be described in terms of universal building blocks. I will review aspects of amplitude factorisation, effects that break it, how they are captured by the shockwave (or Balitsky/JIMWLK) formalism and the extension of this framework to second order in the (rapidity) logarithmic expansion (NNLL). Working at this order, I will discuss the extraction of the two-loop Lipatov vertex and three-loop gluon Regge trajectory in QCD and N=4 super Yang-Mills via matching to recently computed scattering amplitudes.