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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)…

Algebraic Geometry · Mathematics 2020-02-11 Matthias Zach

We give a criterion to test geometric properties such as Whitney equisingularity and Thom's $a_f$ condition for new families of (possibly non-isolated) hypersurface singularities that "behave well" with respect to their Newton diagrams. As…

Algebraic Geometry · Mathematics 2020-05-05 Christophe Eyral , Mutsuo Oka

Let $f\colon X\to\mathbb{A}^1_k$ be a morphism from a smooth variety to an affine line with an isolated singular point. For such a singularity, we have two invariants. One is a non-degenerate symmetric bilinear form (de Rham), and the other…

Algebraic Geometry · Mathematics 2026-04-06 Daichi Takeuchi

We show that the base spaces of the semiuniversal unfoldings of some weighted homogeneous singularities can be identified with moduli spaces of $A_\infty$-structures on the trivial extension algebras of the endomorphism algebras of the…

Algebraic Geometry · Mathematics 2022-03-21 Yanki Lekili , Kazushi Ueda

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…

Algebraic Geometry · Mathematics 2011-11-29 Miriam da Silva Pereira , Maria Aparecida Soares Ruas

In this series of lectures, I will discuss results for complex hypersurfaces with non-isolated singularities. In Lecture 1, I will review basic definitions and results on complex hypersurfaces, and then present classical material on the…

Algebraic Geometry · Mathematics 2015-11-16 David B. Massey

We say that a complex analytic space, $X$, is an intersection cohomology manifold if and only if the shifted constant sheaf on $X$ is isomorphic to intersection cohomology; this is quickly seen to be equivalent to $X$ being a homology…

Algebraic Geometry · Mathematics 2007-05-23 David B. Massey

Let $f : X\to \Delta$ be a $1$-parameter family of $2$-dimensional isolated hypersurface singularities. In this paper, we show that if the Milnor number is constant, then any semistable model, obtained from $f$ after a sufficiently large…

Algebraic Geometry · Mathematics 2023-12-05 Marta Aldasoro Rosales

Let $ \Phi: ({\mathbb C}^2, 0) \to ( {\mathbb C}^3, 0) $ be a finitely determined complex analytic germ and let $(\{f=0\},0)$ be the reduced equation of its image, a non-isolated hypersurface singularity. We provide the plumbing graph of…

Algebraic Geometry · Mathematics 2019-02-05 András Némethi , Gergő Pintér

For an isolated hypersurface singularity $f=0$, the Milnor number $\mu$ is greater than or equal to the Tjurina number $\tau$ (the dimension of the base of the semi-universal deformation), with equality if $f$ is quasi-homogeneous. K. Saito…

Algebraic Geometry · Mathematics 2016-03-28 Jonathan Wahl

In an unpublished lecture note, J. Brian\c{c}on observed that if $\{f_t\}$ is a family of isolated complex hypersurface singularities such that the Newton boundary of $f_t$ is independent of $t$ and $f_t$ is non-degenerate, then the…

Algebraic Geometry · Mathematics 2015-12-15 Christophe Eyral , Mutsuo Oka

An old conjecture of Durfee 1978 bounds the ratio of two basic invariants of complex isolated complete intersection surface singularities: the Milnor number and the singularity (or geometric) genus. We give a counterexample for the case of…

Algebraic Geometry · Mathematics 2011-11-08 Dmitry Kerner , András Némethi

We study versions of homological mirror symmetry for hypersurface cusp singularities and the three hypersurface simple elliptic singularities. We show that the Milnor fibres of each of these carries a distinguished Lefschetz fibration; its…

Symplectic Geometry · Mathematics 2017-05-29 Ailsa Keating

Let $R$ be a discrete valuation ring, with valuation $v \colon R \twoheadrightarrow \mathbb{Z}_{\ge 0} \cup \{\infty\}$ and residue field $k$. Let $H$ be a hypersurface $\operatorname{Proj}(R[x_0,\ldots,x_n]/\langle f \rangle)$. Let $H_k$…

Algebraic Geometry · Mathematics 2025-10-17 Bjorn Poonen , Michael Stoll

We prove that for any germ of complex analytic set in $\CC^n$ there exists a hypersurface singularity whose Milnor fibration has trivial geometric monodromy and fibre homotopic to the complement of the germ of complex analytic set. As an…

Algebraic Geometry · Mathematics 2011-02-17 Javier Fernandez de Bobadilla

This article and its successor concern the topology of real isolated hypersurface singularities. We prove that after attaching a certain number of handles the real Milnor fibres become contractible, with each handle corresponding to a…

Algebraic Geometry · Mathematics 2021-10-12 Lars Andersen

We extend the Hirzebruch-Milnor class of a hypersurface $X$ to the case where the normal bundle is nontrivial and $X$ cannot be defined by a global function, using the associated line bundle and the graded quotients of the monodromy…

Algebraic Geometry · Mathematics 2023-10-31 Laurenţiu Maxim , Morihiko Saito , Ruijie Yang

We introduce spectral Hirzebruch-Milnor classes for singular hypersurfaces. These can be identified with Steenbrink spectra in the isolated singularity case, and may be viewed as their global analogues in general. Their definition uses…

Algebraic Geometry · Mathematics 2017-03-23 Laurentiu Maxim , Morihiko Saito , Joerg Schuermann

A cyclic quotient singularity of type $p^2/pq-1$ ($0<q<p, (p,q)=1$) has a smoothing whose Milnor fibre is a $\mathbb Q$HD, or rational homology disk (i.e., the Milnor number is $0$) ([9], 5.9.1). In the 1980's, we discovered additional…

Algebraic Geometry · Mathematics 2020-06-29 Jonathan Wahl

Explicit formulas determining the dimension and the degree of the singular subscheme of hypersurfaces in ${\mathbb P}^n$ are given in terms of the graded Betti numbers of the minimal free resolution of the corresponding Jacobian algebra.…

Algebraic Geometry · Mathematics 2026-05-05 Alexandru Dimca , Gabriel Sticlaru