English

Computational Paths Form a Weak {\omega}-Groupoid

Logic in Computer Science 2025-12-02 v1

Abstract

Lumsdaine (2010) and van den Berg-Garner (2011) proved that types in Martin-L\"of type theory carry the structure of weak {\omega}-groupoids. Their proofs, while foundational, rely on abstract properties of the identity type without providing explicit computational content for coherence witnesses. We establish an analogous result for computational paths -- an alternative formulation of equality where witnesses are explicit sequences of rewrites from the LNDEQ-TRS term rewriting system. Our main result is that computational paths on any type form a weak {\omega}-groupoid with fully explicit coherence data. The groupoid operations -- identity, composition, and inverse -- are defined at every dimension, and the coherence laws (associativity, unit laws, inverse laws) are witnessed by concrete rewrite derivations rather than abstract existence proofs. The construction provides: (i) a proper tower of n-cells for all dimensions, with 2-cells as derivations between paths and higher cells mediating between lower-dimensional witnesses; (ii) explicit pentagon and triangle coherences built from the rewrite rules; and (iii) contractibility at dimensions 3\geq 3, ensuring all parallel higher cells are connected. The contractibility property is derived from the normalization algorithm of the rewrite system, grounding the higher-dimensional structure in concrete computational content. The entire construction has been formalized in Lean 4, providing machine-checked verification of the weak {\omega}-groupoid structure.

Keywords

Cite

@article{arxiv.2512.00657,
  title  = {Computational Paths Form a Weak {\omega}-Groupoid},
  author = {Arthur F. Ramos and Tiago M. L. de Veras and Ruy J. G. B. de Queiroz and Anjolina G. de Oliveira},
  journal= {arXiv preprint arXiv:2512.00657},
  year   = {2025}
}

Comments

24 pages. Formalized in Lean 4

R2 v1 2026-07-01T08:01:09.770Z