Algebraic integrability of nilpotent planar vector fields

Abstract

We characterize, using normal forms of quasi-homogeneous expansions, the analytic vector fields at nilpotent singular point having an algebraic first integral over the ring C [[ x, y ]] . As a consequence, we provide a link between the algebraic integrability problem and the existence of a formal inverse integrat- ing factor which is null at the singular point.