2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/51017This thesis considers massive field theories in 1+1 dimensions known as affine Toda quantum field theories. We first consider the boundary sine-Gordon model, deriving a complete picture of the boundary bound state structure for general integrable boundary conditions, and then more general ATFTs in the bulk, discovering a "generalised bootstrap" equation which explicitly encodes the Lie algebra into the S-matrix. This last is related to a number of S-matrix identities, as well as a generalisation of the idea that the conserved charges of the theory form an eigenvector of the Cartan matrix.Ph.D. thesis, Durham, LaTeX, 112 pages, 6 eps figures, uses fancyheadings.styHigh Energy Physics - Theorytext