A result on the existence and uniqueness of metric projection for certain sets is proved, by means of a saddle point theorem. A conjecture, based on such a result and aiming for the construction of aâ€¦ (More)

A recent multiplicity theorem for the critical points of a functional defined on a finiteâ€“ dimensional Hilbert space, established by Ricceri, is extended. An application to Dirichlet boundary valueâ€¦ (More)

In this paper we establish a multiplicity result for a second-order non-autonomous system. Using a variational principle of Ricceri we prove that if the set of global minima of a certain function hasâ€¦ (More)

We consider a difference equation involving the discrete p-Laplacian operator, depending on a positive real parameter k. We prove, under convenient assumptions, that for k big enough the equationsâ€¦ (More)

Through variational methods, we study nonautonomous systems of second-order ordinary differential equations with periodic boundary conditions. First, we deal with a nonlinear system, depending on aâ€¦ (More)

Here, Î» is a positive parameter. Particular emphasis is devoted to the question of finding positive solutions to the above problem. The main difficulty, in dealing with this question, comes from theâ€¦ (More)