2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/115544The long-time asymptotics is analyzed for all finite energy solutions to a model U(1)-invariant nonlinear Klein-Gordon equation in one dimension, with the nonlinearity concentrated at a point. Our main result is that each finite energy solution converges as $t\to\pm\infty$ to the set of ``nonlinear eigenfunctions'' $ψ(x)e\sp{-iωt}$.5 pages, 1 figureAnalysis of PDEsDynamical Systems37K; 35B41; 35L; 35Q; 81; 78text