2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/93615Motivated by recent proposals (Bialynicki-Birula, Mycielski; Haag, Bannier; Weinberg; Doebner, Goldin) for nonlinear quantum mechanical evolution equations for pure states some principal difficulties in the framework of usual quantum theory, which is based on its inherent linear structure, are discussed. A generic construction of nonlinear evolution equations through nonlinear gauge transformations is indicated.LaTeX, 5 pages, no figures, Proc. 5th Wigner Symposium (to appear)Quantum Physicstext