The Tropical Moduli Space of Degree-3 Rational Maps

Fuente: arXiv
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Autori principali: Shaska, Tony, Siadat, Mohammad-Reza
Natura: Preprint
Pubblicazione: 2026
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author Shaska, Tony
Siadat, Mohammad-Reza
author_facet Shaska, Tony
Siadat, Mohammad-Reza
contents We construct and study the tropical moduli space \(\mathcal{M}_3^{\mathrm{trop}}\) of degree-$3$ tropical rational maps \(\mathbb{T}\PP^1 \to \mathbb{T}\PP^1\) up to post-composition. Using a combinatorial description in terms of slope sequences, we classify all such maps and show that there are exactly ten combinatorial types. This yields a polyhedral model of \(\mathcal{M}_3^{\mathrm{trop}}\) parametrized by gap lengths between break points. We determine the automorphism groups and obtain a stratification by explicit linear conditions. We also relate the construction to tropical Hurwitz theory and describe a natural compactification via degenerations of the parameters.
format Preprint
id arxiv_https___arxiv_org_abs_2605_15347
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Tropical Moduli Space of Degree-3 Rational Maps
Shaska, Tony
Siadat, Mohammad-Reza
Algebraic Geometry
Combinatorics
14T05, 14D22, 14H10
G.2.1; I.2.6
We construct and study the tropical moduli space \(\mathcal{M}_3^{\mathrm{trop}}\) of degree-$3$ tropical rational maps \(\mathbb{T}\PP^1 \to \mathbb{T}\PP^1\) up to post-composition. Using a combinatorial description in terms of slope sequences, we classify all such maps and show that there are exactly ten combinatorial types. This yields a polyhedral model of \(\mathcal{M}_3^{\mathrm{trop}}\) parametrized by gap lengths between break points. We determine the automorphism groups and obtain a stratification by explicit linear conditions. We also relate the construction to tropical Hurwitz theory and describe a natural compactification via degenerations of the parameters.
title The Tropical Moduli Space of Degree-3 Rational Maps
topic Algebraic Geometry
Combinatorics
14T05, 14D22, 14H10
G.2.1; I.2.6
url https://arxiv.org/abs/2605.15347