On the variety of tritangential planes to a general K3 surface of degree 6 and genus 4 in $\mP^4$

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Autores principales: Ciliberto, Ciro, Verra, Alessandro
Formato: Preprint
Publicado: 2024
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author Ciliberto, Ciro
Verra, Alessandro
author_facet Ciliberto, Ciro
Verra, Alessandro
contents Let $S\subset \mP^4$ be a general K3 surface of degree 6 and genus 4. In this paper we study the irreducible variety $X_S$ of \emph{tritangential planes} to $S$ whose general point is a plane that intersects $S$ in a curvilinear scheme of length six supported at three non collinear points. The variety $X_S$ can be identified as the relevant part of the fixed locus of the so called \emph{Beauville involution} defined on the Hilbert scheme $S[3]$ of 0--dimensional schemes of length three of $S$. In this paper we prove that: (a) $X_S$ has dimension 3, is irreducible and smooth, except for 210 points that are at most of multiplicity 2 for $X_S$; (b) $X_S$, in its natural embedding in the Grassmannian $\mathbb G(2,4)\subset \mP^9$ of planes in $\mP^4$, has degree $152$.
format Preprint
id arxiv_https___arxiv_org_abs_2406_00822
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On the variety of tritangential planes to a general K3 surface of degree 6 and genus 4 in $\mP^4$
Ciliberto, Ciro
Verra, Alessandro
Algebraic Geometry
Let $S\subset \mP^4$ be a general K3 surface of degree 6 and genus 4. In this paper we study the irreducible variety $X_S$ of \emph{tritangential planes} to $S$ whose general point is a plane that intersects $S$ in a curvilinear scheme of length six supported at three non collinear points. The variety $X_S$ can be identified as the relevant part of the fixed locus of the so called \emph{Beauville involution} defined on the Hilbert scheme $S[3]$ of 0--dimensional schemes of length three of $S$. In this paper we prove that: (a) $X_S$ has dimension 3, is irreducible and smooth, except for 210 points that are at most of multiplicity 2 for $X_S$; (b) $X_S$, in its natural embedding in the Grassmannian $\mathbb G(2,4)\subset \mP^9$ of planes in $\mP^4$, has degree $152$.
title On the variety of tritangential planes to a general K3 surface of degree 6 and genus 4 in $\mP^4$
topic Algebraic Geometry
url https://arxiv.org/abs/2406.00822