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Main Authors: Dvorak, Martin, Figueroa-Reid, Tristan, Hamadani, Rida, Hwang, Byung-Hak, Karunus, Evgenia, Kolmogorov, Vladimir, Meiburg, Alexander, Nelson, Alexander, Nelson, Peter, Sandey, Mark, Sergeev, Ivan
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2509.20539
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author Dvorak, Martin
Figueroa-Reid, Tristan
Hamadani, Rida
Hwang, Byung-Hak
Karunus, Evgenia
Kolmogorov, Vladimir
Meiburg, Alexander
Nelson, Alexander
Nelson, Peter
Sandey, Mark
Sergeev, Ivan
author_facet Dvorak, Martin
Figueroa-Reid, Tristan
Hamadani, Rida
Hwang, Byung-Hak
Karunus, Evgenia
Kolmogorov, Vladimir
Meiburg, Alexander
Nelson, Alexander
Nelson, Peter
Sandey, Mark
Sergeev, Ivan
contents Seymour's decomposition theorem is a hallmark result in matroid theory presenting a structural characterization of the class of regular matroids. Formalization of matroid theory faces many challenges, most importantly that only a limited number of notions and results have been implemented so far. In this work, we formalize the proof of the forward (composition) direction of Seymour's theorem for regular matroids. To this end, we develop a library in Lean 4 that implements definitions and results about totally unimodular matrices, vector matroids, their standard representations, regular matroids, and 1-, 2-, and 3-sums of matrices and binary matroids given by their standard representations. Using this framework, we formally state Seymour's decomposition theorem and implement a formally verified proof of the composition direction in the setting where the matroids have finite rank and may have infinite ground sets.
format Preprint
id arxiv_https___arxiv_org_abs_2509_20539
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Composition Direction of Seymour's Theorem for Regular Matroids -- Formally Verified
Dvorak, Martin
Figueroa-Reid, Tristan
Hamadani, Rida
Hwang, Byung-Hak
Karunus, Evgenia
Kolmogorov, Vladimir
Meiburg, Alexander
Nelson, Alexander
Nelson, Peter
Sandey, Mark
Sergeev, Ivan
Combinatorics
Logic in Computer Science
Seymour's decomposition theorem is a hallmark result in matroid theory presenting a structural characterization of the class of regular matroids. Formalization of matroid theory faces many challenges, most importantly that only a limited number of notions and results have been implemented so far. In this work, we formalize the proof of the forward (composition) direction of Seymour's theorem for regular matroids. To this end, we develop a library in Lean 4 that implements definitions and results about totally unimodular matrices, vector matroids, their standard representations, regular matroids, and 1-, 2-, and 3-sums of matrices and binary matroids given by their standard representations. Using this framework, we formally state Seymour's decomposition theorem and implement a formally verified proof of the composition direction in the setting where the matroids have finite rank and may have infinite ground sets.
title Composition Direction of Seymour's Theorem for Regular Matroids -- Formally Verified
topic Combinatorics
Logic in Computer Science
url https://arxiv.org/abs/2509.20539