Guevara, Alfredo2020-10-012020-10-012020-10-012020-09-01http://hdl.handle.net/10012/16421This thesis is devoted to diverse aspects of scattering amplitudes in gauge theory and gravity including interactions with matter particles. In Part I we focus on the applications of massive scattering amplitudes in gravity to the Black Hole two-body problem. For this we construct a classical limit putting especial emphasis on the multipole expansion of certain massive amplitudes, which we will use to model spinning black holes in a large distance effective regime or particle approximation. In Part II we study scattering amplitudes in six dimensions, and construct a compact formula analogous to the four-dimensional Witten-RSV/rational maps formulation. This provides a supersymmetric extension of moduli space localization formulae such as the CHY integral. We explore the cases of Super Yang-Mills and Maximal Supergravity theories, among others.enDoctoral Thesis