Hamiltonian circle action, invariant hypersurface and the complex projective space

Fuente: arXiv
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Main Author: Li, Ping
Format: Preprint
Published: 2025
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author Li, Ping
author_facet Li, Ping
contents Let $M$ be a $2n$-dimensional closed symplectic manifold admitting a Hamiltonian circle action with isolated fixed points. We show that if $M$ contains an $S^1$-invariant symplectic hypersurface $D$ such that $M\setminus D$ is a homology cell, which is satisfied when $M\setminus D$ is contractible, then $M$ and $D$ are homotopy complex projective spaces with standard Chern classes and the $S^1$-representations on the fixed-point set of $(M,D)$ are the same as those arising from the standard linear actions on $(\mathbb{P}^n,\mathbb{P}^{n-1})$, provided that $n \not \equiv 3 \pmod 4$. This can be viewed as the transformation group analogue to a recent result obtained by Peternell and the author, where the latter was conjectured by Fujita more than four decades ago.
format Preprint
id arxiv_https___arxiv_org_abs_2510_19190
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hamiltonian circle action, invariant hypersurface and the complex projective space
Li, Ping
Differential Geometry
Algebraic Topology
Symplectic Geometry
53D05, 57R20, 32Q60, 37B05, 58J20
Let $M$ be a $2n$-dimensional closed symplectic manifold admitting a Hamiltonian circle action with isolated fixed points. We show that if $M$ contains an $S^1$-invariant symplectic hypersurface $D$ such that $M\setminus D$ is a homology cell, which is satisfied when $M\setminus D$ is contractible, then $M$ and $D$ are homotopy complex projective spaces with standard Chern classes and the $S^1$-representations on the fixed-point set of $(M,D)$ are the same as those arising from the standard linear actions on $(\mathbb{P}^n,\mathbb{P}^{n-1})$, provided that $n \not \equiv 3 \pmod 4$. This can be viewed as the transformation group analogue to a recent result obtained by Peternell and the author, where the latter was conjectured by Fujita more than four decades ago.
title Hamiltonian circle action, invariant hypersurface and the complex projective space
topic Differential Geometry
Algebraic Topology
Symplectic Geometry
53D05, 57R20, 32Q60, 37B05, 58J20
url https://arxiv.org/abs/2510.19190