A constructive approach to the double-categorical small object argument
Category Theory
2025-12-15 v1 Logic
Abstract
Bourke and Garner described how to cofibrantly generate algebraic weak factorisation systems by a small double category of morphisms. However they did not give an explicit construction of the resulting factorisations as in the classical small object argument. In this paper we give such an explicit construction, as the colimit of a chain, which makes the result applicable in constructive settings; in particular, our methods provide a constructive proof that the effective Kan fibrations introduced by Van den Berg and Faber appear as the right class of an algebraic weak factorisation system.
Keywords
Cite
@article{arxiv.2512.11692,
title = {A constructive approach to the double-categorical small object argument},
author = {Benno van den Berg and John Bourke and Paul Seip},
journal= {arXiv preprint arXiv:2512.11692},
year = {2025}
}