Abstract:
This is a survey on questions involving algebraic and analytic solubility of the problem of stability of a singular point of a vector field on the plane, and in particular of the problem of distinguishing between a centre and a focus. It is proved that the stability problem on the plane is analytically insoluble.
Bibliography: 30 titles.
Keywords:vector field, monodromic singular point, focus, centre, monodromy transformation, Newton diagram, blow-up of singularities.