A higher-dimensional Van den Essen type formula for projective foliations and applications

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Main Authors: Corrêa, Maurício, Costa, Gilcione Nonato
Format: Preprint
Published: 2024
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author Corrêa, Maurício
Costa, Gilcione Nonato
author_facet Corrêa, Maurício
Costa, Gilcione Nonato
contents Let $F$ be a one-dimensional holomorphic foliation on $\mathbb{P}^n$ such that $W\subset Sing(F)$, where $W$ is a smooth complete intersection variety. We determine and compute the variation of the Milnor number $ μ(F, W)$ under blowups, which depends on the vanishing order of the pullback foliation along the exceptional divisor, as well as on numerical and topological invariants of $W$. This represents a higher-dimensional version of Van den Essen's formula for projective foliations of dimension one. As an application, we obtain a lower bound for the Milnor number of the foliation. Also, we use this formula to show that for a foliation on $\mathbb{P}^n$ that is singular along a smooth curve, there exists a finite number of blow-ups with centers on smooth curves such that the induced foliation has multiplicity equal to 1 and that for generic points of the curves in the final stage, the singularities are elementary. Moreover, we obtain a bound on the maximum number of blow-ups needed to resolve the foliation, depending on the numerical and topological invariants of the curve.
format Preprint
id arxiv_https___arxiv_org_abs_2410_03947
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A higher-dimensional Van den Essen type formula for projective foliations and applications
Corrêa, Maurício
Costa, Gilcione Nonato
Algebraic Geometry
Complex Variables
Dynamical Systems
Let $F$ be a one-dimensional holomorphic foliation on $\mathbb{P}^n$ such that $W\subset Sing(F)$, where $W$ is a smooth complete intersection variety. We determine and compute the variation of the Milnor number $ μ(F, W)$ under blowups, which depends on the vanishing order of the pullback foliation along the exceptional divisor, as well as on numerical and topological invariants of $W$. This represents a higher-dimensional version of Van den Essen's formula for projective foliations of dimension one. As an application, we obtain a lower bound for the Milnor number of the foliation. Also, we use this formula to show that for a foliation on $\mathbb{P}^n$ that is singular along a smooth curve, there exists a finite number of blow-ups with centers on smooth curves such that the induced foliation has multiplicity equal to 1 and that for generic points of the curves in the final stage, the singularities are elementary. Moreover, we obtain a bound on the maximum number of blow-ups needed to resolve the foliation, depending on the numerical and topological invariants of the curve.
title A higher-dimensional Van den Essen type formula for projective foliations and applications
topic Algebraic Geometry
Complex Variables
Dynamical Systems
url https://arxiv.org/abs/2410.03947