Atypical bifurcation for periodic solutions of -Laplacian systems

In this paper, we study the T-periodic solutions of the parameter-dependent -Laplacian equation equation* ( (x') ) '=F (, t, x, x'). equation* Based on the topological degree theory, we present some atypical bifurcation results in the sense of Prodi--Ambrosetti, i. e. , bifurcation of T-periodic solutions from =0. Finally, we propose some applications to Li\'enard-type equations.