Bifurcation of limit cycles from quadratic centers
The purpose of the paper is to determine the maximum number and relative positions of limit cycles which can appear in a quadratic system possessing at least one center under slight quadratic perturbation. Combining the use of the Pontryagin integrals with the theory of rotated vector fields, the authors determine the geometric form of the bifurcation sets for multiple limit cycles and for separatrix cycles.
maximum number and relative positions of limit cycles
scientific article; zbMATH DE number 810062