Many closed $K$-magnetic geodesics on ${\mathbb{S}}^2$

In this paper we adopt an alternative, analytical approach to Arnol’d problem \cite{A1} about the existence of closed and embedded $K$-magnetic geodesics in the round $2$-sphere ${\mathbb{S}}^2$, where $K: \mathbb S^2 \rightarrow \mathbb R$ is a smooth scalar function. In particular, we use Lyapunov-Schmidt finite-dimensional reduction coupled with a local variational formulation in order to get some existence and multiplicity results bypassing the use of symplectic geometric tools such as the celebrated Viterbo’s theorem and Bottkoll results.