Jump of Milnor numbers

具有非形式Milnor纤维的超平面排列

Hyperplane arrangements with non-formal Milnor fibers

本文提出基于multinet结构的组合条件，用于判定超平面排列的Milnor纤维非形式，并构造了具有该性质的无限族单项排列。

Uniform stable radius and Milnor number for non-degenerate isolated complete intersection singularities

We prove that for two germs of analytic mappings $f,g\colon (\mathbb{C}^n,0) \rightarrow (\mathbb{C}^p,0)$ with the same Newton polyhedra which are (Khovanskii) non-degenerate and their zero sets are complete intersections with isolated singularity at the origin, there is a piecewise analytic family $\{f_t\}$ of analytic maps with $f_0=f, f_1=g$ which has a so-called {\it uniform stable radius for the Milnor fibration}. As a corollary, we show that their Milnor numbers are equal. Also, a formula for the Milnor number is given in terms of the Newton polyhedra of the component functions. This is…

Computation of Milnor numbers and critical values at infinity

We describe how to compute topological objects associated to a polynomial map of several complex variables with isolated singularities. These objects are: the affine critical values, the affine Milnor numbers for all irregular fibers, the critical values at infinity, and the Milnor numbers at infinity for all irregular fibers. Then for a family of polynomials we detect parameters where the topology of the polynomials can change. Implementation and examples are given with the computer algebra system Singular.

Invariance of Milnor numbers and topology of complex polynomials

We give a global version of Le-Ramanujam mu-constant theorem for polynomials. Let f_t, (t in [0,1]), be a family of polynomials of n complex variables with isolated singularities, whose coefficients are polynomials in t. We consider the case where some numerical invariants are constant (the affine Milnor number, the Milnor number at infinity, the number of critical values, the number of affine critical values, the number of critical values at infinity). Let n=2, we also suppose the degree of the f_t is a constant, then the polynomials f_0 and f_1 are topologically equivalent. For n>3 we suppos…

Milnor numbers of deformations of semi-quasi-homogeneous plane curve singularities II

We show the possible Milnor numbers of deformations of semi-quasi-homogeneous isolated plane curve singularities. In Theorem 1.1 we list integers can be attained as Milnor numbers of a given semi-quasi-homogeneous singularity.

Motivic Milnor fibers and Jordan normal forms of Milnor monodromies

By calculating the equivariant mixed Hodge numbers of motivic Milnor fibers introduced by Denef-Loeser, we obtain explicit formulas for the Jordan normal forms of Milnor monodromies. The numbers of the Jordan blocks will be described by the Newton polyhedron of the polynomial.

Milnor numbers of deformations of semi-quasi-homogeneous plane curve singularities

The aim of this paper is to show the possible Milnor numbers of deformations of semi-quasi-homogeneous isolated plane curve singularities. Main result states that if $f$ is irreducible and nondegenerate, by deforming $f$ one can attain all Milnor numbers ranging from $μ(f)$ to $μ(f)-r(p-r)$, where $r$ and $p$ are easily computed from the Newton diagram of $f$.

Milnor numbers in deformations of homogeneous singularities

Let f_0 be a plane curve singularity. We study the Minor numbers of singularities in deformations of f_0. We completely describe the set of these Milnor numbers for homogeneous singularities f_0 in the case of non-degenerate deformations and obtain some partial results on this set in the general case.

On deformation with constant Milnor number and Newton polyhedron

We show that every $μ$-constant family of isolated hypersurface singularities satisfying a nondegeneracy condition in the sense of Kouchnirenko, is topologically trivial, also is equimultiple.

Milnor纤维的顶部Betti数的一个下界

A lower bound on the top Betti number of the Milnor fiber

本文给出了解析函数Milnor纤维顶部非零Betti数的下界，该下界由零维Lê数和临界轨迹复链接上消失循环的内部单值化决定。

几何单值、动机Milnor纤维的混合Hodge数与Newton多面体

Geometric monodromies, mixed Hodge numbers of motivic Milnor fibers and Newton polyhedra

本文引入多项式上同调群中局部与全局单值理论，结合环面几何与动机Milnor纤维，用Newton多面体描述等变混合Hodge数。

Milnor数的不变奇点：Chulkov不等式的推广

Milnor number of an invariant singularity: generalization of Chulkov's inequality

本文推广了Chulkov不等式，证明了在有限阿贝尔群作用下不变的函数germ的Milnor数下界，并展示了达到该下界的函数germ的等变稳定性特性。

The image Milnor number and excellent unfoldings

We show three basic properties on the image Milnor number $μ_I(f)$ of a germ $f\colon(\mathbb{C}^{n},S)\rightarrow(\mathbb{C}^{n+1},0)$ with isolated instability. First, we show the conservation of the image Milnor number, from which one can deduce the upper semi-continuity and the topological invariance for families. Second, we prove the weak Mond's conjecture, which says that $μ_I(f)=0$ if and only if $f$ is stable. Finally, we show a conjecture by Houston that any family $f_t\colon(\mathbb{C}^{n},S)\rightarrow(\mathbb{C}^{n+1},0)$ with $μ_I(f_t)$ constant is excellent in Gaffney's sense. By…

Motivic Milnor fibers over complete intersection varieties and their virtual Betti numbers

We study the Jordan normal forms of the local and global monodromies over complete intersection subvarieties of $C^n$ by using the theory of motivic Milnor fibers. The results will be explicitly described by the mixed volumes of the faces of Newton polyhedrons.

Milnor numbers of projective hypersurfaces with isolated singularities

Let V be a projective hypersurface of fixed degree and dimension which has only isolated singular points. We show that, if the sum of the Milnor numbers at the singular points of V is large, then V cannot have a point of large multiplicity, unless V is a cone. As an application, we give an affirmative answer to a conjecture of Dimca and Papadima.

The Milnor-Palamodov Theorem for Functions on Isolated Hypersurface Singularities

In this note we give a simple proof of the following relative analog of the well known Milnor-Palamodov theorem: the Bruce-Roberts number of a function relative to an isolated hypersurface singularity is equal to its topological Milnor number (the rank of a certain relative (co)homology group) if and only if the hypersurface singularity is quasihomogeneous. The proof relies on an interpretation of the Bruce-Roberts number in terms of differential forms and the Lê-Greuel formula.

A bound for the Milnor number of plane curve singularities

Let $f=0$ be a plane algebraic curve of degree $d>1$ with an isolated singular point at the origin of the complex plane. We show that the Milnor number $μ_0(f)$ is less than or equal to $(d-1)^2-\left[\frac{d}{2}\right]$, unless $f=0$ is a set of $d$ concurrent lines passing through 0. Then we characterize the curves $f=0$ for which $μ_0(f)=(d-1)^2-\left[\frac{d}{2}\right]$.

Milnor numbers and Euler obstruction

We determine the relation between the local Euler obstruction $Eu_f$ of a holomorphic function $f$ and different generalizations of the Milnor number for functions on singular spaces.

Calculating Milnor Numbers and Versal Component Dimensions from P-Resolution Fans

We use Altmann's toric fan description of P-resolutions to formulate a new description of deformation theory invariants for two-dimensional cyclic quotient singularities. In particular, we show how to calculate the dimensions of the (reduced) versal base space components as well as Milnor numbers of smoothings over them.

Families of ICIS with constant total Milnor number

We show that a family of isolated complete intersection singularities (ICIS) with constant total Milnor number has no coalescence of singularities. This extends a well known result of Gabrielov, Lazzeri and Lê for hypersurfaces. We use A'Campo's theorem to see that the Lefschetz number of the generic monodromy of the ICIS is zero when the ICIS is singular. We give a pair applications for families of functions on ICIS which extend also some known results for functions on a smooth variety.

Homological index for 1-forms and a Milnor number for isolated singularities

We introduce a notion of a homological index of a holomorphic 1-form on a germ of a complex analytic variety with an isolated singularity, inspired by X. Gómez-Mont and G.-M. Greuel. For isolated complete intersection singularities it coincides with the index defined earlier by two of the authors. Subtracting from this index another one, called radial, we get an invariant of the singularity which does not depend on the 1-form. For isolated complete intersection singularities this invariant coincides with the Milnor number. We compute this invariant for arbitrary curve singularities and compare…

Image Milnor number formulas for weighted-homogeneous map-germs

We give formulas for the image Milnor number of a weighted-homogeneous map-germ $(\mathbb{C}^n,0)\to(\mathbb{C}^{n+1},0)$, for $n=4$ and $5$, in terms of weights and degrees. Our expressions are obtained by a purely interpolative method, applied to a result by Ohmoto. We use our approach to recover the formulas for $n=2$ and $3$ due to Mond and Ohmoto, respectively. For $n\geq 6$, the method is valid as long as certain multi-singularity conjecture holds.

孤立完全交奇点的 Milnor 数与 Tjurina 数

Milnor and Tjurina numbers for an isolated complete intersection singularity

本文证明孤立完全交奇点的 Milnor 数可由仅依赖于 Tjurina 数和维数的存在性界控制，证明基于 arXiv:2204.05594 引入的 A$\mathfrak{m}$AC 方法。

一维局部环的Milnor数

The Milnor Number of One Dimensional Local Rings

本文提出了一维局部环的Milnor数类比，并展示了其与经典ADE奇点半群的关系。

The Milnor number of plane irreducible singularities in positive characteristic

\noindent Let $μ(f)$ resp. $c(f)$ be the Milnor number resp. the degree of the conductor of an irreducible power series $f\in \bK[[x,y]]$, where $\bK$ is an algebraically closed field of characteristic $p\geq 0$. It is well-known that $μ(f)\geq c(f)$. We give necessary and sufficient conditions for the equality $μ(f)=c(f)$ in terms of the semigroup associated with $f$, provided that $p>\ord f$.

The total Milnor number of the weighted-Le-Yomdin-at-infinity polynomial

We give a concrete formula for the total Milnor number of the weighted-Le-Yomdin-at-infinity polynomial in most of the interesting cases. As an application, we give a description of the monodromy fibration at infinity for such kind of polynomial.

Contact exponent and the Milnor number of plane curve singularities

We investigate properties of the contact exponent (in the sense of Hironaka [Hi]) of plane algebroid curve singularities over algebraically closed fields of arbitrary characteristic. We prove that the contact exponent is an equisingularity invariant and give a new proof of the stability of the maximal contact. Then we prove a bound for the Milnor number and determine the equisingularity class of algebroid curves for which this bound is attained. We do not use the method of Newton's diagrams. Our tool is the logarithmic distance developed in [GB-P1].

Milnor fibers and Links of Local Complete Intersections

We discuss and prove a number of cohomological results for Milnor fibers, real links, and complex links of local complete intersections with singularities of arbitrary dimension.

On the quotient of Milnor and Tjurina numbers for two-dimensional isolated hypersurface singularities

In this paper we give a complete answer to a question posed by Dimca and Greuel about the quotient of the Milnor and Tjurina numbers of a plane curve singularity. We put this question into a general framework of the study of the difference of Milnor and Tjurina numbers for isolated complete intersection singularities showing its connection with other problems in singularity theory.

Note on Milnor numbers of irreducible germs

Let $(\bf {V,0})\subset (\mathbb{C}^n,0)$ be a germ of a complex hypersurface and let $f: (\mathbb{C}^n,0)\to(\mathbb{C}^n,0)$ be a germ of a finite holomorphic mapping. If germs $(\bf {V,0})$ and ${\bf W}:=(F^{-1}(\bf{ V})),0)$ are irreducible and with isolated singularities, then $$μ(F^{-1}(\bf{ V}))\ge μ(\bf {V}),$$ where $μ$ denotes the Milnor number.

MAPLE subroutines for computing Milnor and Tyurina numbers of hypersurface singularities with application to Arnol'd adjacencies

In the present paper MAPLE subroutines computing Milnor and Tyurina numbers of an isolated algebraic hypersurface singularity are presented and described in detail. They represents examples, and perhaps the first ones, of a MAPLE implementation of local monomial ordering. As an application, the last section is devoted to writing down equations of algebraic stratifications of Kuranishi spaces of simple Arnol'd singularities: they geometrically represents, by means of inclusions of algebraic subsets, the partial ordering on classes of simple singularities induced by the adjacency relation.

任意特征下超曲面奇点的 Milnor 数

The Milnor number of a hypersurface singularity in arbitrary characteristic

本文研究正特征域上超曲面奇点 Milnor 数在接触等价下的变化，给出其不变性的充要条件，并将其有限性与一般纤维光滑性及平面分支的 conductor 建立联系。

A Lê-Greuel type formula for the image Milnor number

Let $f:(\mathbb{C}^n,0)\rightarrow (\mathbb{C}^{n+1},0)$ be a corank 1 finitely determined map germ. For a generic linear form $p:(\mathbb{C}^{n+1},0)\to(\mathbb{C},0)$ we denote by $g:(\mathbb{C}^{n-1},0)\rightarrow (\mathbb{C}^{n},0)$ the transverse slice of $f$ with respect to $p$. We prove that the sum of the image Milnor numbers $μ_I(f)+μ_I(g)$ is equal to the number of critical points of the stratified Morse function $p|_{X_s}:X_s\to\mathbb{C}$, where $X_s$ is the disentanglement of $f$ (i.e., the image of a stabilisation $f_s$ of $f$).

On the Milnor formula in arbitrary characteristic

The Milnor formula $μ=2δ-r+1$ relates the Milnor number $μ$, the double point number $δ$ and the number $r$ of branches of a plane curve singularity. It holds over the fields of characteristic zero. Melle and Wall based on a result by Deligne proved the inequality $μ\geq 2δ-r+1$ in arbitrary characteristic and showed that the equality $μ=2δ-r+1$ characterizes the singularities with no wild vanishing cycles. In this note we give an account of results on the Milnor formula in characteristic $p$. It holds if the plane singularity is Newton non-degenerate (Boubakri et al. Rev. Mat. Complut. (2010)…

Codimension Two Determinantal Varieties with Isolated Singularities

We study codimension two determinantal varieties with isolated singularities. These singularities admit a unique smoothing, thus we can define their Milnor number as the middle Betti number of their generic fiber. For surfaces in C^4, we obtain a Lê-Greuel formula expressing the Milnor number of the surface in terms of the second polar multiplicity and the Milnor number of a generic section. We also relate the Milnor number with Ebeling and Gusein-Zade index of the 1- form given by the differential of a generic linear projection defined on the surface. To illustrate the results, in the last se…

A generalization of Milnor's formula

We describe a generalization of Milnor's formula for the Milnor number of an isolated hypersurface singularity to the case of a function $f$ whose restriction $f|(X,0)$ to an arbitrarily singular reduced complex analytic space $(X,0) \subset (\mathbb C^n,0)$ has an isolated singularity in the stratified sense. The corresponding analogue of the Milnor number, $μ_f(α;X,0)$, is the number of Morse critical points in a stratum $\mathscr S_α$ of $(X,0)$ in a morsification of $f|(X,0)$. Our formula expresses $μ_f(α;X,0)$ as a homological index based on the derived geometry of the Nash modification o…

关于全纯函数芽对的米尔诺数和蒂尤林数

On Milnor and Tjurina numbers of Pairs of Holomorphic Functions Germs

该研究受全纯函数芽对的米尔诺数分岔公式启发，通过叶状理论引入蒂尤林数，证明其为解析不变量并推导公式及性质，还用此不变量刻画半驯亚纯函数芽，同时研究了全纯函数芽对的米尔诺数相关性质。

小秩的$\boldsymbol{\funA^1}$-米尔诺数的刻画

Characterization of $\mathbb{A}^1$-Milnor numbers of small rank

该研究刻画了小秩$\funA^1$-米尔诺数的性质，明确了特定特征域上格罗滕迪克-维特环元素与$\funA^1$-米尔诺数的对应关系，揭示了二元多项式$\funA^1$-米尔诺数的秩限制及变量约化方法。

广义Milnor数与Tjurina数的商在任意特征下 hypersurface 畸变中的上界

The Quotient of Milnor Number by Tjurina Number of Hypersurface Singularities in Arbitrary Characteristic

本文通过Hilbert-Samuel乘数等工具，建立了任意特征下孤立hypersurface奇异性的广义Milnor数与Tjurina数商的精确上界，并推导出特征零下的上界，证明了孤立表面奇点的μ/τ≤3/2，回应了Almirón猜想并验证了Durfee猜想的弱形式。

Hyperplane arrangements and mixed Hodge numbers of the Milnor fiber

For each complex central essential hyperplane arrangement $\mathcal{A}$, let $F_{\mathcal{A}}$ denote its Milnor fiber. We use Tevelev's theory of tropical compactifications to study invariants related to the mixed Hodge structure on the cohomology of $F_{\mathcal{A}}$. We prove that the map taking each arrangement $\mathcal{A}$ to the Hodge-Deligne polynomial of $F_{\mathcal{A}}$ is locally constant on the realization space of any loop-free matroid. When $\mathcal{A}$ consists of distinct hyperplanes, we also give a combinatorial description for the homotopy type of the boundary complex of an…

Morse theory, Milnor fibers and minimality of hyperplane arrangements

Through the study of Morse theory on the associated Milnor fiber, we show that complex hyperplane arrangement complements are minimal. That is, the complement of a complex hyperplane arrangement has the homotopy type of a CW complex in which the number of p-cells equals the p-th betti number.

Image Milnor number and $\mathscr{A}_e$-codimension for maps between weighted homogeneous irreducible curves

Let $(X,0)\subset (\mathbb{C}^n,0)$ be an irreducible weighted homogeneous singularity curve and let $f:(X,0)\to(\mathbb{C}^2,0)$ be a map germ finite, one-to-one and weighted homogeneous with the same weights of $(X,0)$. We show that $\mathscr{A}_e$-$codim(X,f)=μ_I(f)$, where $\mathscr{A}_e$-$codim(X,f)$ is the $\mathscr{A}_e$-codimension, i.e., the minimum number of parameters in a versal deformation and $μ_I(f)$ is the image Milnor number, i.e., the number of vanishing cycles in the image of a stabilisation of $f$.

Milnor numbers of projective hypersurfaces and the chromatic polynomial of graphs

The chromatic polynomial of a graph G counts the number of proper colorings of G. We give an affirmative answer to the conjecture of Read and Rota-Heron-Welsh that the absolute values of the coefficients of the chromatic polynomial form a log-concave sequence. We define a sequence of numerical invariants of projective hypersurfaces analogous to the Milnor number of local analytic hypersurfaces. Then we give a characterization of correspondences between projective spaces up to a positive integer multiple which includes the conjecture on the chromatic polynomial as a special case. As a byproduct…

任意特征下平面曲线奇点的Milnor数

Milnor number of plane curve singularities in arbitrary characteristic

本研究将Kouchnirenko公式推广至任意退化幂级数，并推广García Barroso和Płoski的猜想，特别利用Greuel和Nguyen的结果在某些情形下证明了该猜想。

Addendum to the paper "Characteristic Cycles of Perverse Sheaves and Milnor Fibers"

We note that Theorem 5.4 of the paper ``Characteristic cycles of perverse sheaves and Milnor fibers" (by P. Nang and K. Takeuchi, published online in Math. Zeitschrift, October 15, 2004) holds for "any" non-zero complex number $a$.

关于实 Milnor 数在渐近 Lipschitz 等价下的不变性

On the Invariance of the Real Milnor Number under Asymptotically Lipschitz Equivalence

本文研究了函数芽在双 Lipschitz 及渐近 Lipschitz 等价下实 Milnor 数的不变性，引入 $α$-导数研究渐近增长，并确立了该数在 $C^k$ 和 $C^{\infty}$ 等价下保持不变的充分条件。

On combinatorial invariance of the cohomology of Milnor fiber of arrangements and Catalan equation over function field

We discuss combinatorial invariance of the betti numbers of the Milnor fiber for arrangements of lines with points of multiplicity at most three and describe a link between this problem and enumeration of solutions of the Catalan equation over function field in the case when its coefficients are products of linear forms and the equation defines an elliptic curve.

Topological invariants and Milnor fibre for $\mathcal{A}$-finite germs $\mathbb{C}^2\to\mathbb{C}^3$

This note is the observation that a simple combination of known results shows that the usual analytic invariants of a finitely determined multi-germ $f\colon (\mathbb{C}^2,S)\to(\mathbb{C}^3,0)$ ---namely the image Milnor number $μ_I$, the number of crosscaps and triple points, $C$ and $T$, and the Milnor number $μ(Σ)$ of the curve of double points in the target--- depend only on the embedded topological type of the image of $f$. As a consequence one obtains the topological invariance of the sign-refined Smale invariant for immersions $j\colon S^3\looparrowright S^5$ associated to finitely det…

具有驯值域半群的平面分支的Milnor数

The Milnor Number of Plane Branches With Tame Semigroup of Values

本文研究任意特征代数闭域上平面分支的Milnor数，证明当值半群为驯顺半群（域特征不整除其极小生成元）时，Milnor数仍与半群导子相等，弥补了正特征域下原结论不成立的缺口。

Double coverings of arrangement complements and $2$-torsion in Milnor fiber homology

We prove that the mod $2$ Betti numbers of double coverings of a complex hyperplane arrangement complement are combinatorially determined. The proof is based on a relation between the mod $2$ Aomoto complex and the transfer long exact sequence. Applying the above result to the icosidodecahedral arrangement ($16$ planes in the three dimensional space related to the icosidodecahedron), we conclude that the first homology of the Milnor fiber has non-trivial $2$-torsion.

向量场Milnor数的下界

A lower bound for the Milnor number of vector fields

本文研究了包含局部完全交光滑正维成分的全纯向量场，推导了其Milnor数的下界，并通过显式族展示最优性及奇点的重新分布机制。

Solvable Groups, Free Divisors and Nonisolated Matrix Singularities II: Vanishing Topology

In this paper we use the results from the first part to compute the vanishing topology for matrix singularities based on certain spaces of matrices. We place the variety of singular matrices in a geometric configuration of free divisors which are the "exceptional orbit varieties" for repesentations of solvable groups. Because there are towers of representations for towers of solvable groups, the free divisors actually form a tower of free divisors $E_n$, and we give an inductive procedure for computing the vanishing topology of the matrix singularities. The inductive procedure we use is an ext…

Newton polygons and families of polynomials

We consider a continuous family $(f_s)$, $s\in[0,1]$ of complex polynomials in two variables with isolated singularities, that are Newton non-degenerate. We suppose that the Euler characteristic of a generic fiber is constant (or equivalently the sum of the affine Milnor number and the Milnor number at infinity $μ(s)+λ(s)$ is constant). We firstly prove that the set of critical values at infinity depends continuously on $s$, and secondly that the degree of the $f_s$ is constant (up to an algebraic automorphism of $\Cc^2$).

关于叶状结构的第 k 个 Milnor 数与第 k 个 Tjurina 数

On the k-th Milnor and k-th Tjurina Numbers of a Foliation

本文引入并系统研究了全纯叶状结构的第 k 个 Milnor 数与第 k 个 Tjurina 数，建立显式公式与拓扑性质，解决并反驳了相关猜想，还推广了 Teissier 引理并给出拟齐次情形的闭公式。