2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53049Eugene Wigner showed already in 1939 that the elementary particles are related to the irreducible representations of the Poincare algebra. In the light-cone frame formulation of quantum field theory one can extend these representations to depend also on a coupling constant. The representations then become non-linear and contain the interaction terms which are shown to have strong uniqueness. Extending the algebra to supersymmetry it is shown that two field theories stick out, N=4 Yang-Mills and N=8 Supergravity and their higher dimensional analogues. I also discuss string theory from this starting point.Lecture presented at the Poincare Symposium held in Brussels on October 8-9, 2004High Energy Physics - Theorytext