Twelve Limit Cycles in a Cubic Order Planar System with Z2-symmetry
نویسندگان
چکیده
In this paper, we report the existence of twelve small limit cycles in a planar system with 3rd-degree polynomial functions. The system has Z2symmetry, with a saddle point, or a node, or a focus point at the origin, and two focus points which are symmetric about the origin. It is shown that such a Z2-equivariant vector field can have twelve small limit cycles. Fourteen or sixteen small limit cycles, as expected before, cannot not exist.
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