Almost All Transverse-Free Plane Curves Are Trivially Transverse-Free

Fuente: arXiv
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Auteurs principaux: Lopez, Alejandro, Villarreal, Bella, Watson, Ren, Whyte, Jaedon
Format: Preprint
Publié: 2025
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author Lopez, Alejandro
Villarreal, Bella
Watson, Ren
Whyte, Jaedon
author_facet Lopez, Alejandro
Villarreal, Bella
Watson, Ren
Whyte, Jaedon
contents Call a curve $C \subset \mathbb{P}^2$ defined over $\mathbb{F}_q$ transverse-free if every line over $\mathbb{F}_q$ intersects $C$ at some closed point with multiplicity at least 2. In 2004, Poonen used a notion of density to treat Bertini Theorems over finite fields. In this paper we develop methods for density computation and apply them to estimate the density of the set of polynomials defining transverse-free curves. In order to do so, we use a combinatorial approach based on blocking sets of $\operatorname{PG}(2, q)$ and prove an upper bound on the number of such sets of fixed size $< 2q$. We thus obtain that nearly all transverse-free curves contain singularities at every $\mathbb{F}_q$-point of some line.
format Preprint
id arxiv_https___arxiv_org_abs_2502_00549
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Almost All Transverse-Free Plane Curves Are Trivially Transverse-Free
Lopez, Alejandro
Villarreal, Bella
Watson, Ren
Whyte, Jaedon
Algebraic Geometry
Combinatorics
11G20, 51E20, 51E21
Call a curve $C \subset \mathbb{P}^2$ defined over $\mathbb{F}_q$ transverse-free if every line over $\mathbb{F}_q$ intersects $C$ at some closed point with multiplicity at least 2. In 2004, Poonen used a notion of density to treat Bertini Theorems over finite fields. In this paper we develop methods for density computation and apply them to estimate the density of the set of polynomials defining transverse-free curves. In order to do so, we use a combinatorial approach based on blocking sets of $\operatorname{PG}(2, q)$ and prove an upper bound on the number of such sets of fixed size $< 2q$. We thus obtain that nearly all transverse-free curves contain singularities at every $\mathbb{F}_q$-point of some line.
title Almost All Transverse-Free Plane Curves Are Trivially Transverse-Free
topic Algebraic Geometry
Combinatorics
11G20, 51E20, 51E21
url https://arxiv.org/abs/2502.00549