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Cubical approximation for directed topology, II

Sanjeevi Krishnan

Algebraic & Geometric Topology 26 (2026) 135–199
DOI: 10.2140/agt.2026.26.135
Abstract

We establish an equivalence between directed homotopy categories of (diagrams of) cubical sets and (diagrams of) directed topological spaces. This equivalence both lifts and extends an equivalence between classical homotopy categories of cubical sets and topological spaces. Some simple applications include combinatorial descriptions and subsequent calculations of directed homotopy monoids and directed singular 1-cohomology monoids. Another application is a characterization of isomorphisms between small categories up to zigzags of natural transformations as directed homotopy equivalences between directed classifying spaces. Cubical sets throughout the paper are taken to mean presheaves over the minimal symmetric monoidal variant of the cube category. Along the way, we characterize morphisms in this variant as the interval-preserving lattice homomorphisms between finite Boolean lattices.

Keywords
directed homotopy, cubical approximation
Mathematical Subject Classification
Primary: 06B99, 54E99, 55P99, 55U99
References
Publication
Received: 29 September 2023
Revised: 10 January 2025
Accepted: 6 February 2025
Published: 16 January 2026
Authors
Sanjeevi Krishnan
Department of Mathematics
The Ohio State University
Columbus, OH
United States

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