The worst destabilizing 1-parameter subgroup for toric rational curves with one unibranch singularity

Fuente: arXiv
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Main Authors: Jackson, Joshua, Swinarski, David
Format: Preprint
Published: 2025
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author Jackson, Joshua
Swinarski, David
author_facet Jackson, Joshua
Swinarski, David
contents Kempf proved that when a point is unstable in the sense of Geometric Invariant Theory, there is a ``worst'' destabilizing 1-parameter subgroup $λ^{*}$. It is natural to ask: what are the worst 1-PS for the unstable points in the GIT problems used to construct the moduli space of curves $\overline{M}_g$? Here we consider Chow points of toric rational curves with one unibranch singular point. We translate the problem as an explicit problem in convex geometry (finding the closest point on a polyhedral cone to a point outside it). We prove that the worst 1-PS has a combinatorial description that persists once the embedding dimension is sufficiently large, and present some examples.
format Preprint
id arxiv_https___arxiv_org_abs_2502_00458
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The worst destabilizing 1-parameter subgroup for toric rational curves with one unibranch singularity
Jackson, Joshua
Swinarski, David
Algebraic Geometry
14L24 (Primary) 14H20, 14Q05 (Secondary)
Kempf proved that when a point is unstable in the sense of Geometric Invariant Theory, there is a ``worst'' destabilizing 1-parameter subgroup $λ^{*}$. It is natural to ask: what are the worst 1-PS for the unstable points in the GIT problems used to construct the moduli space of curves $\overline{M}_g$? Here we consider Chow points of toric rational curves with one unibranch singular point. We translate the problem as an explicit problem in convex geometry (finding the closest point on a polyhedral cone to a point outside it). We prove that the worst 1-PS has a combinatorial description that persists once the embedding dimension is sufficiently large, and present some examples.
title The worst destabilizing 1-parameter subgroup for toric rational curves with one unibranch singularity
topic Algebraic Geometry
14L24 (Primary) 14H20, 14Q05 (Secondary)
url https://arxiv.org/abs/2502.00458