A Eudoxian study of discriminant curves associated to normal surface singularities

Fuente: arXiv
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Auteurs principaux: Barroso, Evelia Rosa García, Popescu-Pampu, Patrick
Format: Preprint
Publié: 2024
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author Barroso, Evelia Rosa García
Popescu-Pampu, Patrick
author_facet Barroso, Evelia Rosa García
Popescu-Pampu, Patrick
contents Let $(f,g): (S,s) \to (\mathbb{C}^2, 0)$ be a finite morphism from a germ of normal complex analytic surface to the germ of $\mathbb{C}^2$ at the origin. We show that the affine algebraic curve in $\mathbb{C}^2$ defined by the initial Newton polynomial of a defining series of the discriminant germ of $(f,g)$ depends up to toric automorphisms only on the germs of curves defined by $f$ and $g$. This result generalizes a theorem of Gryszka, Gwoździewicz and Parusiński, which is the special case in which $(S,s)$ is smooth. Our proof uses a common generalization of formulas of Lê, Casas-Alvero and Némethi for the intersection number of the discriminant with a germ of plane curve. It uses also a theorem of Delgado and Maugendre characterizing the special members of pencils of curves on normal surface singularities. We apply it to the pencils generated by all pairs $(f^b, g^a)$, for varying positive integral exponents $a, b$, following a strategy initiated by Gwoździewicz and by Delgado and Maugendre. This is similar to the Eudoxian method of comparison of magnitudes by comparing the sizes of their positive integral multiples.
format Preprint
id arxiv_https___arxiv_org_abs_2410_21250
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A Eudoxian study of discriminant curves associated to normal surface singularities
Barroso, Evelia Rosa García
Popescu-Pampu, Patrick
Algebraic Geometry
14B05, 14H20
Let $(f,g): (S,s) \to (\mathbb{C}^2, 0)$ be a finite morphism from a germ of normal complex analytic surface to the germ of $\mathbb{C}^2$ at the origin. We show that the affine algebraic curve in $\mathbb{C}^2$ defined by the initial Newton polynomial of a defining series of the discriminant germ of $(f,g)$ depends up to toric automorphisms only on the germs of curves defined by $f$ and $g$. This result generalizes a theorem of Gryszka, Gwoździewicz and Parusiński, which is the special case in which $(S,s)$ is smooth. Our proof uses a common generalization of formulas of Lê, Casas-Alvero and Némethi for the intersection number of the discriminant with a germ of plane curve. It uses also a theorem of Delgado and Maugendre characterizing the special members of pencils of curves on normal surface singularities. We apply it to the pencils generated by all pairs $(f^b, g^a)$, for varying positive integral exponents $a, b$, following a strategy initiated by Gwoździewicz and by Delgado and Maugendre. This is similar to the Eudoxian method of comparison of magnitudes by comparing the sizes of their positive integral multiples.
title A Eudoxian study of discriminant curves associated to normal surface singularities
topic Algebraic Geometry
14B05, 14H20
url https://arxiv.org/abs/2410.21250