Electroweak Physics at Very High Energy

Aim of the thesis is to review the main quantum field theory tools that are needed to deal with electroweak interactions in the very high energy regime, far above the electroweak scale, and to apply them to a concrete calculation. These tools include the equivalence theorem and the resummation of infrared enhanced effects like the electroweak Sudakov double logarithms. The latter ones are particularly relevant in the case of electroweak interactions because they persist also in inclusive observables, producing sizeable and peculiar effects that change the nature of electroweak physics in very high energy reactions. These effects might be relevant also at the LHC, and they will become essential at future high energy colliders. Concrete applications studied in the thesis will be the prediction of cross-sections at lepton colliders with tenths of TeV center of mass energy, including the production of hypothetical heavy particles via vector boson fusion.