Projective models for Hilbert squares of $K3$ surfaces

Fuente: arXiv
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Autori principali: Ortiz, Ángel David Ríos, Rojas, Andrés, Song, Jieao
Natura: Preprint
Pubblicazione: 2025
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author Ortiz, Ángel David Ríos
Rojas, Andrés
Song, Jieao
author_facet Ortiz, Ángel David Ríos
Rojas, Andrés
Song, Jieao
contents For a very general polarized $K3$ surface $S\subset \mathbb{P}^g$ of genus $g\ge 5$, we study the linear system on the Hilbert square $S^{[2]}$ parametrizing quadrics in $\mathbb{P}^g$ that contain $S$. We prove its very ampleness for $g\geq 7$. In the cases of genus 7 or 8, we describe in detail the projective geometry of the corresponding embedding by making use of the Mukai model for $S$. In both cases, it can be realized as a degeneracy locus on an ambient homogeneous space, in a strikingly similar fashion. In consequence, we give explicit descriptions of its ideal and syzygies. Furthermore, we extract new information on the locally complete families, in a first step towards the understanding of their projective geometry.
format Preprint
id arxiv_https___arxiv_org_abs_2510_02065
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Projective models for Hilbert squares of $K3$ surfaces
Ortiz, Ángel David Ríos
Rojas, Andrés
Song, Jieao
Algebraic Geometry
14J28, 14J42, 14M12
For a very general polarized $K3$ surface $S\subset \mathbb{P}^g$ of genus $g\ge 5$, we study the linear system on the Hilbert square $S^{[2]}$ parametrizing quadrics in $\mathbb{P}^g$ that contain $S$. We prove its very ampleness for $g\geq 7$. In the cases of genus 7 or 8, we describe in detail the projective geometry of the corresponding embedding by making use of the Mukai model for $S$. In both cases, it can be realized as a degeneracy locus on an ambient homogeneous space, in a strikingly similar fashion. In consequence, we give explicit descriptions of its ideal and syzygies. Furthermore, we extract new information on the locally complete families, in a first step towards the understanding of their projective geometry.
title Projective models for Hilbert squares of $K3$ surfaces
topic Algebraic Geometry
14J28, 14J42, 14M12
url https://arxiv.org/abs/2510.02065