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An explanation is given for the initially surprising ubiquity of separating sets in normal complex surface germs. It is shown that they are quite common in higher dimensions too. The relationship between separating sets and the geometry of…

Algebraic Geometry · Mathematics 2011-07-29 Lev Birbrair , Alexandre Fernandes , Walter D Neumann

In this paper we study bilipschitz equivalences of germs of holomorphic foliations in $(\mathbb{C}^2,0)$. We prove that the algebraic multiplicity of a singularity is invariant by such equivalences. Moreover, for a large class of…

Dynamical Systems · Mathematics 2016-01-26 Rudy Rosas

We proof here the existence of a topological thick and thin decomposition of any closed definable thick isolated singularity germ in the spirit of the recently discovered metric thick and thin decomposition of complex normal surface…

Metric Geometry · Mathematics 2012-08-22 Lev Birbrair , Alexandre Fernandes , Vincent Grandjean

We investigate the relationships between the Lipschitz outer geometry and the embedded topological type of a hypersurface germ in $(\mathbb C^n,0)$. It is well known that the Lipschitz outer geometry of a complex plane curve germ determines…

Algebraic Geometry · Mathematics 2015-11-26 Walter D. Neumann , Anne Pichon

We prove that a map germ $f:(\mathbb{C}^n,S)\to(\mathbb{C}^{n+1},0)$ with isolated instability is stable if and only if $\mu_I(f)=0$, where $\mu_I(f)$ is the image Milnor number defined by Mond. In a previous paper we proved this result…

Algebraic Geometry · Mathematics 2022-07-06 R. Giménez Conejero , J. J. Nuño-Ballesteros

We provide bi-Lipschitz invariants for finitely determined map germs $f: (\mathbb{K}^n,0) \to (\mathbb{K}^p, 0)$, where $\mathbb{K} = \mathbb{R}$ or $ \mathbb{C}$. The aim of the paper is to provide partial answers to the following…

Geometric Topology · Mathematics 2025-09-23 Jean-paul Brasselet , Maria Aparecida Soares Ruas , Thuy Nguyen

We produce examples of complex algebraic surfaces with isolated singularities such that these singularities are not metrically conic, i.e. the germs of the surfaces near singular points are not bi-Lipschitz equivalent, with respect to the…

Algebraic Geometry · Mathematics 2007-05-23 Lev Birbrair , Alexandre Fernandes

We prove that for any two definable germs in a polynomially bounded o-minimal structure, there exists a critical threshold $\alpha_0 \in (0,1)$ such that if these germs are bi-$\alpha$-H"older equivalent for some $\alpha \ge \alpha_0$, then…

Algebraic Geometry · Mathematics 2025-12-29 An V. Q. Huynh , Minh B. Nguyen , Nhan X. V. Nguyen , Minh Q. Vu

Consider the germ of an isolated surface singularity in $(\mC^3,0)$. The corresponding Milnor fibre possesses the homology lattice (the integral middle homology with a natural symmetric intersection form). An old question of A.Durfee (1978)…

Algebraic Geometry · Mathematics 2010-10-21 Dmitry Kerner , Andras Nemethi

The germ of an algebraic variety is naturally equipped with two different metrics up to bilipschitz equivalence. The inner metric and the outer metric. One calls a germ of a variety Lipschitz normally embedded if the two metrics are…

Algebraic Geometry · Mathematics 2016-07-27 Helge Møller Pedersen , Maria Aparecida Soares Ruas

We consider germs of holomorphic vector fields with an isolated singularity at the origin $0\in\mathbb{C}^2$. We introduce a notion of stability, similar to "Lyapunov stability". For such a germ, called $L$-stable singularity, either the…

Dynamical Systems · Mathematics 2016-01-29 Victor Leon , Bruno Scardua

We study normal forms of germs of singular real-analytic Levi-flat hypersurfaces. We prove the existence of rigid normal forms for singular Levi-flat hypersurfaces which are defined by the vanishing of the real part of complex…

Complex Variables · Mathematics 2018-10-16 Arturo Fernández-Pérez , Gustavo Marra

We show that for every $k\ge 3$ there exist complex algebraic cones of dimension $k$ with isolated singularities, which are bi-Lipschitz and semi-algebraically equivalent but they have different degrees. We also prove that homeomorphic…

Algebraic Geometry · Mathematics 2023-09-14 Alexandre Fernandes , Zbigniew Jelonek , José Edson Sampaio

In this paper, we prove Fukui-Kurdyka-Paunescu's Conjecture, which says that subanalytic arc-analytic bi-Lipschitz homeomorphisms preserve the multiplicities of real analytic sets. We also prove several other results on the invariance of…

Algebraic Geometry · Mathematics 2021-08-18 Alexandre Fernandes , Zbigniew Jelonek , José Edson Sampaio

We study the boundary L_t of the Milnor fiber for the non-isolated singularities in C^3 with equation z^m - g(x,y) = 0 where g(x,y) is a non-reduced plane curve germ. We give a complete proof that L_t is a Waldhausen graph manifold and we…

Algebraic Geometry · Mathematics 2007-05-23 Francoise Michel , Anne Pichon , Claude Weber

Any germ of a complex analytic space is equipped with two natural metrics: the outer metric induced by the hermitian metric of the ambient space and the inner metric, which is the associated riemannian metric on the germ. These two metrics…

Algebraic Geometry · Mathematics 2019-09-25 Walter D Neumann , Helge Møller Pedersen , Anne Pichon

We study multi-parameters deformations of isolated singularity function-germs on either a subanalytic set or a complex analytic spaces. We prove that if such a deformation has no coalescing of singular points, then it has constant…

Complex Variables · Mathematics 2022-06-22 Aurélio Menegon , Miriam da Silva Pereira

We show that two bi-Lipschitz equivalent Brieskorn-Pham hypersurfaces have the same multiplicities at $0$. Moreover we show that if two algebraic $(n-1)$-dimensional cones $P, R\subset\mathbb C^n$ with isolated singularities are…

Algebraic Geometry · Mathematics 2024-04-11 Alexandre Fernandes , Zbigniew Jelonek , José Edson Sampaio

The Milnor number, \mu(X,0), and the singularity genus, p_g(X,0), are fundamental invariants of isolated hypersurface singularities (more generally, of local complete intersections). The long standing Durfee conjecture (and its…

Algebraic Geometry · Mathematics 2017-05-23 Dmitry Kerner , András Némethi

We study the Euler characteristic of the Milnor fibre of a hypersurface singularity. This invariant is given in terms of the Euler characteristic of a fibre in between the original singularity and its Milnor fibre and in terms of the Euler…

Algebraic Geometry · Mathematics 2008-07-04 Kevin Houston