English

A strong desingularization theorem

Algebraic Geometry 2007-05-23 v1

Abstract

Let XX be a closed subscheme embedded in a scheme WW smooth over a field k{\bf k} of characteristic zero, and let I(X){\mathcal I}(X) be the sheaf of ideals defining XX. Assume that the set of regular points of XX is dense in XX. We prove that there exists a proper, birational morphism, π:WrW\pi: W_r\longrightarrow W, obtained as a composition of monoidal transformations, so that if XrWrX_r\subset W_r denotes the strict transform of XWX\subset W then: 1) The morphism π:WrW\pi:W_r\longrightarrow W is an embedded desingularization of XX (as in Hironaka's Theorem); 2) The {\em total transform} of I(X){\mathcal I}(X) in OWr{\mathcal O}_{W_r} factors as a product of an invertible sheaf of ideals L{\mathcal L} supported on the exceptional locus, and the sheaf of ideals defining the strict transform of XX (i.e. I(X)OWr=LI(Xr){\mathcal I}(X){\mathcal O}_{W_r}={\mathcal L}\cdot{\mathcal I}(X_r)). This result is stronger than Hironaka's Theorem, in fact (2) is novel and does not hold for desingularizations which follow Hironaka's line of proof unless XX is a hypersurface. We will say that WrWW_r\longrightarrow W defines a {\em Strong Desingularization of XX}.

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Cite

@article{arxiv.math/0104001,
  title  = {A strong desingularization theorem},
  author = {Ana Bravo and Orlando Villamayor},
  journal= {arXiv preprint arXiv:math/0104001},
  year   = {2007}
}

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31 pages