Numerical control over complex analytic singularities
Author(s)
Bibliographic Information
Numerical control over complex analytic singularities
（Memoirs of the American Mathematical Society, no. 778）
American Mathematical Society, 2003
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Includes bibliographical references (p. 261-266) and index
"May 2003, volume 163, number 778 (end of volume)"
Description and Table of Contents
Description
The Milnor number is a powerful invariant of an isolated, complex, affine hyper surface singularity. It provides data about the local, ambient, topological-type of the hyper surface, and the constancy of the Milnor number throughout a family implies that Thom's $a_f$ condition holds and that the local, ambient, topological-type is constant in the family. Much of the usefulness of the Milnor number is due to the fact that it can be effectively calculated in an algebraic manner.The Le cycles and numbers are a generalization of the Milnor number to the setting of complex, affine hyper surface singularities, where the singular set is allowed to be of arbitrary dimension. As with the Milnor number, the Le numbers provide data about the local, ambient, topological-type of the hyper surface, and the constancy of the Le numbers throughout a family implies that Thom's $a_f$ condition holds and that the Milnor fibrations are constant throughout the family. Again, much of the usefulness of the Le numbers is due to the fact that they can be effectively calculated in an algebraic manner.In this work, we generalize the Le cycles and numbers to the case of hyper surfaces inside arbitrary analytic spaces. We define the Le-Vogel cycles and numbers, and prove that the Le-Vogel numbers control Thom's $a_f$ condition. We also prove a relationship between the Euler characteristic of the Milnor fibre and the Le-Vogel numbers. Moreover, we give examples which show that the Le-Vogel numbers are effectively calculable. In order to define the Le-Vogel cycles and numbers, we require, and include, a great deal of background material on Vogel cycles, analytic intersection theory, and the derived category. Also, to serve as a model case for the Le-Vogel cycles, we recall our earlier work on the Le cycles of an affine hyper surface singularity.
Table of Contents
Overview Part I. Algebraic Preliminaries: Gap Sheaves and Vogel Cycles: Introduction Gap sheaves Gap cycles and Vogel cycles The Le-Iomdine-Vogel formulas Summary of Part I Part II. Le Cycles and Hypersurface Singularities: Introduction Definitions and basic properties Elementary examples A handle decomposition of the Milnor fibre Generalized Le-Iomdine formulas Le numbers and hyperplane arrangements Thom's $a_f$ condition Aligned singularities Suspending singularities Constancy of the Milnor fibrations Another characterization of the Le cycles Part III. Isolated Critical Points of Functions on Singular Spaces: Introduction Critical avatars The relative polar curve The link between the algebraic and topological points of view The special case of perverse sheaves Thom's $a_f$ condition Continuous families of constructible complexes Part IV. Non-Isolated Critical Points of Functions on Singular Spaces: Introduction Le-Vogel cycles Le-Iomdine formulas and Thom's condition Le-Vogel cycles and the Euler characteristic Appendix A. Analytic cycles and intersections Appendix B. The derived category Appendix C. Privileged neighborhoods and lifting Milnor fibrations References Index.
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