Scattering of Charge Carriers in 2+1-Dimensional Quantum Field Theory

Abstract: The aim of this thesis is to examine the hard $S$-matrix for QED and QCD, due to Hannesdottir and Schwartz [1], both recreating known results, and finding new results in lower dimensions. Electrons by themselves are not gauge invariant, and in the massless limit do not give finite $S$-matrix elements for individual processes; one needs to add together seemingly arbitrary combinations of diagrams in order to be able to calculate the scattering cross-section. One remedy is to exchange the bare electron for a dressed state, or equivalently to include the dressing in the $S$-matrix itself. This gives rise to a formalism in which one needs only consider time cuts of an individual diagram in order to find finite $S$-matrix elements. The main result of this thesis is the examination of the results which are found by Hannesdottir and Schwartz in a model system of fewer dimensions. This may be of use for toy model calculations in QCD, where 2+1-dimensional QED better models certain phenomena than does 3+1-dimensional QED.