arXiv subjects

Jaroslaw Wlodarczyk

Publications and source records attributed to Jaroslaw Wlodarczyk.

7 recordsLinked to original sources

arXiv2016

Singular implicit and inverse function theorems. Strong resolution with normally flat centers

Building upon ideas of Hironaka, Bierstone-Milman, Malgrange and others we generalize the inverse and implicit function theorem (in differential, analytic and algebraic setting) to sets of functions of larger multiplicities (or ideals). This allows one to describe singularities given by a finite set of generators or by ideals in a simpler form. In the special Cohen-Macaulay case we obtain a singular analog of the inverse function theorem. The singular implicit function theorem is closely related to a (proven here) extended version of the Weierstrass-Hironaka-Malgrange division and preparation theorems. The primary motivation for this paper comes from the desingularization problem. As an illustration of the techniques used, we give some applications of our theorems to desingularization extending some results on Hironaka normal flatness, the Samuel stratification and the Hilbert-Samuel function. The notion of the standard basis along Samuel stratum introduced in the paper (inspired by the Bierstone-Milman and Hironaka constructions) allows us to describe singularities along the Samuel stratum in a relatively simple way. It leads to a canonical reduction of the strong Hironaka desingularization with normally flat centers to a so called resolution of marked ideals. Moreover, in characteristic zero, the standard basis along Samuel stratum generates a unique canonical Rees algebra along Samuel startum giving a straightforward proof of the strong desingularization in algebraic and analytic cases.

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arXiv2016

Equisingular resolution with SNC fibers and combinatorial type of varieties

We introduce the notion of combinatorial type of varieties $X$ which generalizes the concept of the dual complex of SNC divisors. It is a unique, up to homotopy, finite simplicial complex $Σ(X)$ which is functorial with respect to morphisms of varieties. Its cohomology $H^i(Σ(X),Q)$ for complex projective varieties coincide with weight zero part of the Deligne filtration $W_0(H^i(X,Q))$. The notion can be understood as a topological measure of the singularities of algebaric schemes of finite type. We also prove that any variety in characteristic zero admits the Hironaka desingularization with all fibers having SNC. Moreover the dual complexes of the fibers are isomorphic on strata. Also for any morphism $f:X\to Y$ there exists a similar desingularization $\tilde{X}\to X$ for which the induce morphism $\tilde{X}\to Y$ has SNC fibers. One of the consequence is that for any projective morphism $f:X\to Y$ the combinatorial type of the fiber is a constructible function. In particular $\dim(W_0H^i(f^{-1}(y))$ is constructible.

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arXiv2012

Effective Hironaka resolution and its Complexity (with appendix on applications in positive characteristic)

Building upon works of Hironaka, Bierstone-Milman, Villamayor and Wlodarczyk, we give an a priori estimate for the complexity of the simplified Hironaka algorithm. As a consequence of this result, we show that there exists canonical Hironaka embedded desingularization and principalization over fields of large characteristic (relative to the degrees of generating polynomials).

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arXiv2006

Simple Constructive Weak Factorization

We give a simplified algorithm of the functorial weak factorization of birational morphisms of nonsingular varieties over a field of characteristic zero into a composite of blow-ups and blow-downs with smooth centers.

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arXiv2004

Simple Hironaka resolution in characteristic zero

Building upon work of Villamayor and Bierstone-Milman we give a proof of the canonical Hironaka principalization and desingularization. The idea of "homogenized ideals" introduced in the paper gives {\it a priori} the canonicity of algorithm and radically simplifies the proof.

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arXiv2002

Toroidal varieties and the weak Factorization Theorem

The main goal of the present paper is two-fold. First we extend the theory of toroidal embeddings introduced by Kempf, Knudsen, Mumford and Saint-Donat to the class of toroidal varieties with stratifications (which is the main body of the paper). Second we give a proof of the following weak factorization theorem as an application and illustration of the theory: A birational map between complete nonsingular varieties over an algebraically closed field K of characteristic zero is a composite of blow ups and blow downs with smooth centers. Another proof of the weak factorization theorem appeared in a joint paper with Abramovich, Karu and Matsuki (math.AG/9904135) In that paper the theorem is stated and proven in general for proper algebraic and analytic spaces.

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arXiv1999

Birational cobordisms and factorization of birational maps

In this paper we develop a Morse-like theory in order to decompose birational maps and morphisms of smooth projective varieties defined over a field of characteristic zero into more elementary steps which are locally étale isomorphic to equivariant flips, blow-ups and blow-downs of toric varieties. A crucial role in the considerations is played by K^*-actions where K is the base field. This paper serves as a basis for proving the weak factorization conjecture on factorization of birational maps in characteristic zero into blow-ups and blow-downs. This is carried out in two subsequent papers, one by the author (Combinatorial structures on toroidal varieties: a proof of the weak Factorization Theorem) and one joint with Abramovich, Karu and Matsuki (Torification and factorization of birational maps). In the last paper, the ideas of the present paper are discussed using geometric invariant theory.

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