2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/163861We review our proof that in a scaling limit, the time evolution of a quantum particle in a static random environment leads to a diffusion equation. In particular, we discuss the role of Feynman graph expansions and of renormalization.Contribution to the proceedings of the conference in honour of Wolfhart Zimmermann's 80th birthday, Ringberg Castle, February 3-6, 2008. LaTeX, 16 pages with 6 figuresMathematical Physics60J65; 81T18; 82C10; 82C44text