2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90111We argue that usual quantum statics and the dynamical equivalence of mixed quantum states to {\it probabilistic mixtures}suffice to guarantee a linear evolution law, which necessarily complies with the no-signaling condition. Alternatively, there are nonlinear dynamical extensions that treat mixed states as {\it elementary mixtures} and evolve {\it every}pure state linearly and unitarily. But if all {\it entangled} pure states evolve linearly, then elementary mixtures cannot evolve nonlinearly without challenging quantum locality. Conversely, any such extension that is relativistically well behaved demands a nonlinear evolution [decoherence] of pure entangled states. Wherefrom follows that the linear evolution of entangled pure states provides an unequivocal signature of linear quantum dynamics.Latex2e/RevTex4; 5 pgs; submitted to Phys.Lett.A. Sec.4 removed and superseded by quant-ph/0207042. Sec.3 now includes argument on equivalence of "remote preparation" to "projection postulate", and a well-behaved nonlinear example for illustrationQuantum Physicstext