Atypical bifurcation for periodic solutions of φ-Laplacian systems

In this paper, we study the T-periodic solutions of the parameter-dependent φ-Laplacian equation {equation*} (φ(x'))'=F(λ,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 λ=0. Finally, we propose some applications to Li\'enard-type equations.