Centers and limit cycles of vector fields defined on invariant spheres

Abstract

The aim of this paper is the study of the center-focus and cyclicity problems inside the class X of 3-dimensional vector fields that admit a first integral that leaves invariant any sphere centered at the origin. We classify the centers of linear, quadratic homogeneous and a family of quadratic vector fields F ⊂ X, restricted to one of these spheres. Moreover, we show the existence of at least 4 limit cycles in family F.