Nilpotent Holomorphic Foliations on $(\mathbb{C}^n,\mathbf{0})$

TL;DR

This paper investigates nilpotent holomorphic foliations in complex dimensions, characterizing their structure via pullbacks of Takens' normal form and establishing criteria involving Newton polyhedra for foliations with cuspidal separatrices.

Contribution

It generalizes the classification of nilpotent foliations to higher dimensions and introduces a new criterion using Newton polyhedra for identifying generalized hypersurface type foliations.

Findings

Foliations can be described as pullbacks of Takens' normal form.

Characterization of foliations with quasi-ordinary cuspidal separatrices.

Equivalence of Newton polyhedra for certain foliations and their separatrices.

Abstract

In this paper, we study nilpotent holomorphic foliations in complex dimension $n+1$, at the origin, defined by germs of integrable 1-forms whose linear part is given by \(zdz\). These foliations generalize the classical nilpotent foliations in dimension two. We show that every nilpotent foliation in higher dimensions can be described as the pullback of Takens' normal form, which naturally leads to the existence of cuspidal hypersurfaces as invariant sets. We focus on the case where the separatrix is a quasi-ordinary cuspidal hypersurface, and we provide a characterization of those foliations that are of generalized hypersurface type. Furthermore, we recall the Newton polyhedron of a foliation and prove that, for foliations with a quasi-ordinary cuspidal separatrix, being of generalized hypersurface type is equivalent to the coincidence of the Newton polyhedra of the foliation and its separatrix. This provides a new criterion that extends previous results studied by Fern\'andez-S\'anchez and J. Mozo (2006), and later partially generalized by the second-named author.