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A class of non-rational surface singularities with bijective Nash map

Camille Plénat, Patrick Popescu-Pampu (2006)

Bulletin de la Société Mathématique de France

Let ( 𝒮 , 0 ) be a germ of complex analytic normal surface. On its minimal resolution, we consider the reduced exceptional divisor E and its irreducible components E i , i I . The Nash map associates to each irreducible component C k of the space of arcs through 0 on 𝒮 the unique component of E cut by the strict transform of the generic arc in C k . Nash proved its injectivity and asked if it was bijective. As a particular case of our main theorem, we prove that this is the case if E · E i < 0 for any  i I .

A combinatorial approach to singularities of normal surfaces

Sandro Manfredini (2003)

Annali della Scuola Normale Superiore di Pisa - Classe di Scienze

In this paper we study generic coverings of 2 branched over a curve s.t. the total space is a normal analytic surface, in terms of a graph representing the monodromy of the covering, called monodromy graph. A complete description of the monodromy graphs and of the local fundamental groups is found in case the branch curve is { x n = y m } (with n m ) and the degree of the cover is equal to n or n - 1 .

A note on singularities at infinity of complex polynomials

Adam Parusiński (1997)

Banach Center Publications

Let f be a complex polynomial. We relate the behaviour of f “at infinity” to the sheaf of vanishing cycles of the family f ¯ of projective closures of fibres of f. We show that the absence of such cycles: (i) is equivalent to a condition on the asymptotic behaviour of gradient of f known as Malgrange’s Condition, (ii) implies the C -triviality of f. If the support of sheaf of vanishing cycles of f ¯ is a finite set, then it detects precisely the change of the topology of the fibres of f. Moreover, in...

A supplement to the Iomdin-Lê theorem for singularities with one-dimensional singular locus

Mihai Tibăr (1996)

Banach Center Publications

To a germ f : ( n , 0 ) ( , 0 ) with one-dimensional singular locus one associates series of isolated singularities f N : = f + l N , where l is a general linear function and N . We prove an attaching result of Iomdin-Lê type which compares the homotopy types of the Milnor fibres of f N and f. This is a refinement of the Iomdin-Lê theorem in the general setting of a singular underlying space.

An Algebraic Formula for the Index of a Vector Field on an Isolated Complete Intersection Singularity

H.-Ch. Graf von Bothmer, Wolfgang Ebeling, Xavier Gómez-Mont (2008)

Annales de l’institut Fourier

Let ( V , 0 ) be a germ of a complete intersection variety in n + k , n > 0 , having an isolated singularity at 0 and X be the germ of a holomorphic vector field having an isolated zero at 0 and tangent to V . We show that in this case the homological index and the GSV-index coincide. In the case when the zero of X is also isolated in the ambient space n + k we give a formula for the homological index in terms of local linear algebra.

An inequality for symplectic fillings of the link of a hypersurface K3 singularity

Hiroshi Ohta, Kaoru Ono (2009)

Banach Center Publications

Some relations between normal complex surface singularities and symplectic fillings of the links of the singularities are discussed. For a certain class of singularities of general type, which are called hypersurface K3 singularities in this paper, an inequality for numerical invariants of any minimal symplectic fillings of the links of the singularities is derived. This inequality can be regarded as a symplectic/contact analog of the 11/8-conjecture in 4-dimensional topology.

Coxeter elements for vanishing cycles of types  A 1 2  and  D 1 2

Kyoji Saito (2011)

Annales de l’institut Fourier

We introduce two entire functions f A 1 2 and f D 1 2 in two variables. Both of them have only two critical values 0 and 1 , and the associated maps C 2 C define topologically locally trivial fibrations over C { 0 , 1 } . All critical points in the singular fibers over 0 and 1 are ordinary double points, and the associated vanishing cycles span the middle homology group of the general fiber, whose intersection diagram forms bi-partitely decomposed infinite quivers of type A 1 2 and D 1 2 , respectively. Coxeter elements of type A 1 2 and...

Decompositions of hypersurface singularities oftype J k , 0

Piotr Jaworski (1994)

Annales Polonici Mathematici

Applications of singularity theory give rise to many questions concerning deformations of singularities. Unfortunately, satisfactory answers are known only for simple singularities and partially for unimodal ones. The aim of this paper is to give some insight into decompositions of multi-modal singularities with unimodal leading part. We investigate the J k , 0 singularities which have modality k - 1 but the quasihomogeneous part of their normal form only depends on one modulus.

Deformation of polar methods

David B. Massey, Dirk Siersma (1992)

Annales de l'institut Fourier

We study deformations of hypersurfaces with one-dimensional singular loci by two different methods. The first method is by using the Le numbers of a hypersurfaces singularity — this falls under the general heading of a “polar” method. The second method is by studying the number of certain special types of singularities which occur in generic deformations of the original hypersurface. We compare and contrast these two methods, and provide a large number of examples.

Equimultiple Locus of Embedded Algebroid Surfaces and Blowing–up in Characteristic Zero

Piedra-Sánchez, R., Tornero, J. (2004)

Serdica Mathematical Journal

2000 Mathematics Subject Classification: 14B05, 32S25.The smooth equimultiple locus of embedded algebroid surfaces appears naturally in many resolution processes, both classical and modern. In this paper we explore how it changes by blowing–up.* Supported by FQM 304 and BFM 2000–1523. ** Supported by FQM 218 and BFM 2001–3207.

Equisingular generic discriminants and Whitney conditions

Eric Dago Akéké (2008)

Annales de la faculté des sciences de Toulouse Mathématiques

The purpose of this article is to show that the Whitney conditions are satisfied for complex analytic families of normal surface singularities for which the generic discriminants are equisingular. According to J. Briançon and J. P. Speder the constancy of the topological type of a family of surface singularities does not imply Whitney conditions in general. We will see here that for a family of minimal normal surface singularities these two equisingularity conditions are equivalent.

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