Degenerate Chenciner bifurcation revisited

Generic results for degenerate Chenciner (generalized Neimark-Sacker) bifurcation are obtained in the present work. The bifurcation arises in two-dimensional discrete-time systems with two independent parameters. We define in this work a new transformation of parameters, which enables the study of the bifurcation when the degeneracy occurs. By the four bifurcation diagrams we obtain, new behaviors hidden by the degeneracy are brought to light.