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Main Authors: Zhang, Chencheng, Lu, Xue-Song, Zhang, Pu
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2604.22186
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author Zhang, Chencheng
Lu, Xue-Song
Zhang, Pu
author_facet Zhang, Chencheng
Lu, Xue-Song
Zhang, Pu
contents Homotopic morphisms of $\mathbb E$-triangles in extriangulated categories are introduced. Any morphism of $\mathbb E$-triangles is a composition of homotopic morphisms. Any morphism $(α_1, α_2, α_3)$ of $\mathbb E$-triangles can be modified to be homotopic, by changing one of $α_i$; moreover, all the 15 cases where $α_i$ is an $\mathbb E$-inflation ($\mathbb E$-deflation) are analyzed. Some diagram theorems, especially $4\times 4$ Lemma and its $14$ variants, including $3\times 3$ diagram and Horseshoe Lemma, are investigated. A relation between homotopic morphisms and (middling) good morphisms in triangulated categories are given. Weakly idempotent complete extriangulated categories are characterized.
format Preprint
id arxiv_https___arxiv_org_abs_2604_22186
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Homotopic morphisms and diagram theorems in extriangulated categories
Zhang, Chencheng
Lu, Xue-Song
Zhang, Pu
Category Theory
Homotopic morphisms of $\mathbb E$-triangles in extriangulated categories are introduced. Any morphism of $\mathbb E$-triangles is a composition of homotopic morphisms. Any morphism $(α_1, α_2, α_3)$ of $\mathbb E$-triangles can be modified to be homotopic, by changing one of $α_i$; moreover, all the 15 cases where $α_i$ is an $\mathbb E$-inflation ($\mathbb E$-deflation) are analyzed. Some diagram theorems, especially $4\times 4$ Lemma and its $14$ variants, including $3\times 3$ diagram and Horseshoe Lemma, are investigated. A relation between homotopic morphisms and (middling) good morphisms in triangulated categories are given. Weakly idempotent complete extriangulated categories are characterized.
title Homotopic morphisms and diagram theorems in extriangulated categories
topic Category Theory
url https://arxiv.org/abs/2604.22186