arXiv subjects

J. Fernández de Bobadilla

Publications and source records attributed to J. Fernández de Bobadilla.

4 recordsLinked to original sources

arXiv2024

The Brasselet-Schürmann-Yokura conjecture on $L$-classes of singular varieties

In 2010, Brasselet, Schürmann and Yokura conjectured an equality of characteristic classes of singular varieties between the Goresky-MacPherson $L$-class $L_*(X)$ and the Hirzebruch homology class $T_{1*}(X)$ for a compact complex algebraic variety $X$ that is a rational homology manifold. In this note we give a proof of this conjecture for projective varieties based on cubical hyperresolutions, the Decomposition Theorem, and Hodge theory. The crucial step of the proof is a new characterization of rational homology manifolds in terms of cubical hyperresolutions which we find of independent interest.

math.AG↗

arXiv2020

Topological invariants and Milnor fibre for $\mathcal{A}$-finite germs $\mathbb{C}^2\to\mathbb{C}^3$

This note is the observation that a simple combination of known results shows that the usual analytic invariants of a finitely determined multi-germ $f\colon (\mathbb{C}^2,S)\to(\mathbb{C}^3,0)$ ---namely the image Milnor number $μ_I$, the number of crosscaps and triple points, $C$ and $T$, and the Milnor number $μ(Σ)$ of the curve of double points in the target--- depend only on the embedded topological type of the image of $f$. As a consequence one obtains the topological invariance of the sign-refined Smale invariant for immersions $j\colon S^3\looparrowright S^5$ associated to finitely determined map germs $(\mathbb{C}^2,0)\to(\mathbb{C}^3,0)$. This note is a corrected version of a previous homonymous work containing an error. A previous wrong computation of $b_1(\mathbb{F})$, spotted by Siersma, has been replaced by the correct statement, due to Van Straten. This has forced the proofs for the mentioned topological invariances to differ significantly from the previous version.

math.AG↗

arXiv2016

A Jacobian module for disentanglements and applications to Mond's conjecture

Given a germ of holomorphic map $f$ from $\mathbb C^n$ to $\mathbb C^{n+1}$, we define a module $M(f)$ whose dimension over $\mathbb C$ is an upper bound for the $\mathscr A$-codimension of $f$, with equality if $f$ is weighted homogeneous. We also define a relative version $M_y(F)$ of the module, for unfoldings $F$ of $f$. The main result is that if $(n,n+1)$ are nice dimensions, then the dimension of $M(f)$ over $\mathbb C$ is an upper bound of the image Milnor number of $f$, with equality if and only if the relative module $M_y(F)$ is Cohen-Macaulay for some stable unfolding $F$. In particular, if $M_y(F)$ is Cohen-Macaulay, then we have Mond's conjecture for $f$. Furthermore, if $f$ is quasi-homogeneous, then Mond's conjecture for $f$ is equivalent to the fact that $M_y(F)$ is Cohen-Macaulay. Finally, we observe that to prove Mond's conjecture, it suffices to prove it in a suitable family of examples.

math.AG↗

arXiv2004

On rational cuspidal projective plane curves

In the open problem of classification of rational cuspidal plane curves it is essential to find good necessary conditions on the type of singularities of a curve C in order C to exit. Motivated by the study of the Seiberg-Witten invariant of normal surface singularities whose link is a rational homology sphere we have found good candidates for such necessary conditions. In this paper we study this compatibility conditions and proved them for all curves whose logarithmic Kodaira dimension is strictly less than 2.

math.AG↗