On the paucity of lattice triangles

Fuente: arXiv
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Main Authors: Angdinata, David Kurniadi, Chen, Evan, Ono, Ken, Zhang, Jiaxin, Zhang, Jujian
Format: Preprint
Published: 2026
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_version_ 1866918407635468288
author Angdinata, David Kurniadi
Chen, Evan
Ono, Ken
Zhang, Jiaxin
Zhang, Jujian
author_facet Angdinata, David Kurniadi
Chen, Evan
Ono, Ken
Zhang, Jiaxin
Zhang, Jujian
contents A rational triangle $T$ (one whose angles are rational multiples of $π$) unfolds to a translation surface $(X_T,ω_T)$. The lattice triangle problem asks to classify those $T$ for which $(X_T,ω_T)$ is a Veech (lattice) surface, which means that the $\operatorname{SL}_2(\mathbb R)$-orbit of $(X_T,ω_T)$ is closed in its stratum (so its projection to moduli space is a Teichmüller curve). The most mysterious regime is the "hard obtuse window" (largest angle in $(π/2,2π/3]$), where it is conjectured that no lattice triangles exist. Using an arithmetic reformulation of the Mirzakhani-Wright rank obstruction, we prove a quantitative theorem that rules out all but a density 0 subset of the triangles in this window. The main engine in this paper was autoformalized by AxiomProver in Lean (using mathlib).
format Preprint
id arxiv_https___arxiv_org_abs_2603_23928
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the paucity of lattice triangles
Angdinata, David Kurniadi
Chen, Evan
Ono, Ken
Zhang, Jiaxin
Zhang, Jujian
Dynamical Systems
Combinatorics
Number Theory
37E35, 30F60
A rational triangle $T$ (one whose angles are rational multiples of $π$) unfolds to a translation surface $(X_T,ω_T)$. The lattice triangle problem asks to classify those $T$ for which $(X_T,ω_T)$ is a Veech (lattice) surface, which means that the $\operatorname{SL}_2(\mathbb R)$-orbit of $(X_T,ω_T)$ is closed in its stratum (so its projection to moduli space is a Teichmüller curve). The most mysterious regime is the "hard obtuse window" (largest angle in $(π/2,2π/3]$), where it is conjectured that no lattice triangles exist. Using an arithmetic reformulation of the Mirzakhani-Wright rank obstruction, we prove a quantitative theorem that rules out all but a density 0 subset of the triangles in this window. The main engine in this paper was autoformalized by AxiomProver in Lean (using mathlib).
title On the paucity of lattice triangles
topic Dynamical Systems
Combinatorics
Number Theory
37E35, 30F60
url https://arxiv.org/abs/2603.23928