Smooth plane curves with a unique outer Galois point and their automorphism groups

Fuente: arXiv
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Main Authors: Badr, Eslam, Harui, Takeshi
Format: Preprint
Published: 2026
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author Badr, Eslam
Harui, Takeshi
author_facet Badr, Eslam
Harui, Takeshi
contents We consider smooth plane curves $\mathcal{X}$ of degree $d\geq4$, defined over an algebraically closed field of characteristic $0$, that possess a unique outer Galois point. This geometric condition forces the curve to be a cyclic covering of the projective line, and ensures that its automorphism group fits into a specific theoretical framework. For each possible non-cyclic reduced automorphism group $\operatorname{Aut}_{\operatorname{red}}(\mathcal{X})$, we fully characterize the defining equation of $\mathcal{X}$ and the precise structure of its full automorphism group $\operatorname{Aut}(\mathcal{X})$. This comprehensive analysis not only identifies the exact form of the equation for each automorphism type but also establishes the detailed criteria under which these scenarios can occur, thereby offering a complete classification of defining equations for smooth plane curves with a unique outer Galois point and a non-cyclic reduced automorphism group.
format Preprint
id arxiv_https___arxiv_org_abs_2603_26180
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Smooth plane curves with a unique outer Galois point and their automorphism groups
Badr, Eslam
Harui, Takeshi
Algebraic Geometry
14H37, 14H45, 14H50, 14H10
We consider smooth plane curves $\mathcal{X}$ of degree $d\geq4$, defined over an algebraically closed field of characteristic $0$, that possess a unique outer Galois point. This geometric condition forces the curve to be a cyclic covering of the projective line, and ensures that its automorphism group fits into a specific theoretical framework. For each possible non-cyclic reduced automorphism group $\operatorname{Aut}_{\operatorname{red}}(\mathcal{X})$, we fully characterize the defining equation of $\mathcal{X}$ and the precise structure of its full automorphism group $\operatorname{Aut}(\mathcal{X})$. This comprehensive analysis not only identifies the exact form of the equation for each automorphism type but also establishes the detailed criteria under which these scenarios can occur, thereby offering a complete classification of defining equations for smooth plane curves with a unique outer Galois point and a non-cyclic reduced automorphism group.
title Smooth plane curves with a unique outer Galois point and their automorphism groups
topic Algebraic Geometry
14H37, 14H45, 14H50, 14H10
url https://arxiv.org/abs/2603.26180