Automorphisms of punctual Hilbert schemes and symmetric powers of varieties

Fuente: arXiv
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Main Authors: Bansal, Ashima, Sarkar, Supravat, Vats, Shivam
Format: Preprint
Published: 2025
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author Bansal, Ashima
Sarkar, Supravat
Vats, Shivam
author_facet Bansal, Ashima
Sarkar, Supravat
Vats, Shivam
contents We classify complex smooth projective surfaces whose punctual Hilbert scheme has a non-natural automorphism preserving the big diagonal. This completely answers a question raised by Belmans, Oberdieck and Rennemo, and extends previous works by Boissi{è}re-Sarti, Hayashi, Sasaki, Girardet and Wang. We reduce this to studying the existence of non-natural automorphisms of symmetric powers. We study this question for higher dimensional varieties too, giving some sufficient conditions guaranteeing every automorphism of a symmetric power to be natural. As a corollary, we characterize smooth projective surfaces of Kodaira dimension $\geq 1$ whose punctual Hilbert scheme has a non-natural automorphism, this time not assuming the automorphism preserves the big diagonal. We also address the question, when a smooth projective variety is determined up to isomorphism by its punctual Hilbert scheme.
format Preprint
id arxiv_https___arxiv_org_abs_2508_18059
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Automorphisms of punctual Hilbert schemes and symmetric powers of varieties
Bansal, Ashima
Sarkar, Supravat
Vats, Shivam
Algebraic Geometry
14J50
We classify complex smooth projective surfaces whose punctual Hilbert scheme has a non-natural automorphism preserving the big diagonal. This completely answers a question raised by Belmans, Oberdieck and Rennemo, and extends previous works by Boissi{è}re-Sarti, Hayashi, Sasaki, Girardet and Wang. We reduce this to studying the existence of non-natural automorphisms of symmetric powers. We study this question for higher dimensional varieties too, giving some sufficient conditions guaranteeing every automorphism of a symmetric power to be natural. As a corollary, we characterize smooth projective surfaces of Kodaira dimension $\geq 1$ whose punctual Hilbert scheme has a non-natural automorphism, this time not assuming the automorphism preserves the big diagonal. We also address the question, when a smooth projective variety is determined up to isomorphism by its punctual Hilbert scheme.
title Automorphisms of punctual Hilbert schemes and symmetric powers of varieties
topic Algebraic Geometry
14J50
url https://arxiv.org/abs/2508.18059