Perturbations of graphics with semi-hyperbolic singularities
A very interesting study of the cyclicity of semi-hyperbolic points is done. Namely, bifurcations of limit cycles in the neighbourhood of elementary graphics whose vertices are semi-hyperbolic points of finite codimension are dealt with. The result is first obtained for graphics with two vertices, then generalized. Fine calculus is done, much in the spirit of R. Roussarie (see the bibliography), but also very ingenious. Among the elementary singular points (hyperbolic, elliptic and semi-hyperbolic), semi-hyperbolic vertices are the most difficult to study.
scientific article; zbMATH DE number 1013719