Infinitely many homoclinic orbits for Hamiltonian systems with group symmetries.
Infinitely many periodic solutions for nonautonomous sublinear second-order Hamiltonian systems.
Involutions of real intervals
This paper shows a simple construction of continuous involutions of real intervals in terms of continuous even functions. We also study smooth involutions defined by symmetric equations. Finally, we review some applications, in particular a characterization of isochronous potentials by means of smooth involutions.