2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/185480We find the spectrum of boundary bound states for the sine-Gordon model with Dirichlet boundary conditions, closing the bootstrap and providing a complete description of all the poles in the boundary reflection factors. The boundary Coleman-Thun mechanism plays an important role in the analysis. Two basic lemmas are introduced which should hold for any 1+1-dimensional boundary field theory, allowing the general method to be applied to other models.26 pages, LaTeX2e, uses amsfonts.sty. V2: typos corrected, and equation numbering changed to agree with published versionHigh Energy Physics - Theorytext