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math.DS2026
Quartic polynomial differential systems with three disjoint invariant circles
Chen Cao, Jaume Llibre
We determine the normal forms of real planar polynomial differential systems of degree at most four with three prescribed pairwise disjoint invariant circles, covering all configur…
math.DS2026
New criteria for upper bounds on the number of limit cycles in Liénard systems
Chen Cao, Hebai Chen, Yilei Tang
We establish criteria for at most one or at most two limit cycles of generalized Liénard systems in a single potential well. Two independent uniqueness tests use modified quotients…