We prove several results on lower bounds for the periods of periodic solutions of some classes of functional-differential equations in Hilbert and Banach spaces and difference inclusions in Hilbert spaces.
In this paper, by using the topological degree theory for multivalued maps and the method of guiding functions in Hilbert spaces we deal with the existence of periodic oscillations for a class of feedback control systems in Hilbert spaces.
The purpose of this paper is to study the existence of periodic solutions for the non-autonomous second order Hamiltonian system Some new existence theorems are obtained by the least action principle.
This paper deals with the system of functional-differential equations where is a linear bounded operator, , and and are spaces of -dimensional -periodic vector functions with continuous and integrable on components, respectively. Conditions which guarantee the existence of a unique -periodic solution and continuous dependence of that solution on the right hand side of the system considered are established.