Un problema di Stefan a due fasi con condizione di flusso non lineare sulla parte fissa della frontiera è affrontato mediante la teoria dei semigruppi di contrazione in . Si dimostra l'esistenza e l’unicità della soluzione nel senso di Crandall-Liggett e Bénilan.
Let be domain in a complex Banach space , and let be a pseudometric assigned to by a Schwarz-Pick system. In the first section of the paper we establish several criteria for a mapping to be a generator of a -nonexpansive semigroup on in terms of its nonlinear resolvent. In the second section we let be a complex Hilbert space, the open unit ball of , and the hyperbolic metric on . We introduce the notion of a -monotone mapping and obtain simple characterizations of generators...
In the paper the concept of a controllable continuous flow in a metric space is introduced as a generalization of a controllable system of differential equations in a Banach space, and various kinds of stability and of boundedness of this flow are defined. Theorems stating necessary and sufficient conditions for particular kinds of stability and boundedness are formulated in terms of Ljapunov functions.
For a hybrid system composed of a cable with masses at both ends, we prove the existence of solutions for a class of nonlinear and nonmonotone feedback laws by means of a priori estimates. Assuming some local monotonicity, strong stabilization is obtained thanks to some Riemann's invariants technique and La Salle's principle.