2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198790We review and summarize recent works on the relation between form factors in integrable quantum field theory and deformation of geometrical data associated to hyper-elliptic curves. This relation, which is based on a deformation of the Riemann bilinear identity, in particular leads to the notion of null vectors in integrable field theory and to a new description of the KdV hierarchy.17 pages, LaTeX, for the proceedings of the conference "Advanced Quantum Field Theory (in memory of Claude Itzykson)", Lalonde, France, Sept. 96High Energy Physics - TheoryQuantum Algebratext