Variational approach for weak quasiperiodic solutions of quasiperiodically excited Lagrangian systems on Riemannian manifolds

We apply a variational method to prove the existence of weak Besicovitch quasiperiodic solutions for natural Lagrangian system on Riemannian manifold with time-quasiperiodic force function. In contrast to previous papers, our approach does not require non-positiveness condition for sectional Riemannian curvature. As an application of obtained results, we find conditions for the existence of weak quasiperiodic solutions in spherical pendulum system under quasiperiodic forcing.