The $d$-gonal locus in the moduli space of tropical plane curves

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Main Authors: Leitz, Desmond, Morrison, Ralph, Newman-Taylor, Søren, Wang, Vincent X.
Format: Preprint
Published: 2025
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_version_ 1866918218245865472
author Leitz, Desmond
Morrison, Ralph
Newman-Taylor, Søren
Wang, Vincent X.
author_facet Leitz, Desmond
Morrison, Ralph
Newman-Taylor, Søren
Wang, Vincent X.
contents We introduce and study the locus $\mathbb{M}_{g,d}^\textrm{nd}$ of genus $g$ tropical plane curves of gonality $d$ inside the moduli space $\mathbb{M}^{\textrm{nd}}_{g}$ of tropical plane curves of genus $g$. Each such tropical curve arises from a Newton polygon, and we conjecture that the gonality of the tropical curve is equal to an easily computed parameter of this polygon called the expected gonality, closely related to the lattice width of the polygon. Let $\mathbb{M}_{g,{\underline{d}}}^\textrm{nd}$ denote the locus of tropical curves whose associated Newton polygon has expected gonality $d$. We prove that for fixed $d$ and sufficiently large genus $g$, the dimensions of these two loci agree: \[ \\dim\left(\mathbb{M}_{g,d}^\textrm{nd}\right) =\dim\left(\mathbb{M}_{g,{\underline{d}}}^\textrm{nd}\right). \] Our results provide evidence that, in sufficiently high genus compared to expected gonality, the gonality of a tropical curve is determined by the expected gonality of the Newton polygon from which it arises.
format Preprint
id arxiv_https___arxiv_org_abs_2511_20805
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The $d$-gonal locus in the moduli space of tropical plane curves
Leitz, Desmond
Morrison, Ralph
Newman-Taylor, Søren
Wang, Vincent X.
Combinatorics
Algebraic Geometry
14T05, 52B20, 14H10
We introduce and study the locus $\mathbb{M}_{g,d}^\textrm{nd}$ of genus $g$ tropical plane curves of gonality $d$ inside the moduli space $\mathbb{M}^{\textrm{nd}}_{g}$ of tropical plane curves of genus $g$. Each such tropical curve arises from a Newton polygon, and we conjecture that the gonality of the tropical curve is equal to an easily computed parameter of this polygon called the expected gonality, closely related to the lattice width of the polygon. Let $\mathbb{M}_{g,{\underline{d}}}^\textrm{nd}$ denote the locus of tropical curves whose associated Newton polygon has expected gonality $d$. We prove that for fixed $d$ and sufficiently large genus $g$, the dimensions of these two loci agree: \[ \\dim\left(\mathbb{M}_{g,d}^\textrm{nd}\right) =\dim\left(\mathbb{M}_{g,{\underline{d}}}^\textrm{nd}\right). \] Our results provide evidence that, in sufficiently high genus compared to expected gonality, the gonality of a tropical curve is determined by the expected gonality of the Newton polygon from which it arises.
title The $d$-gonal locus in the moduli space of tropical plane curves
topic Combinatorics
Algebraic Geometry
14T05, 52B20, 14H10
url https://arxiv.org/abs/2511.20805