Presenting the topological stratified homotopy hypothesis
Lukas Waas
TL;DR
The paper addresses the stratified homotopy hypothesis by unifying three prominent theories of stratified spaces through model-categorical presentations. It develops left semi-model structures on $\textnormal{Strat}$ that present Douteau-Henriques, Haine, and Nand-Lal's theories and proves a Quillen equivalence between the semi-model category presenting Nand-Lal's theory and a left Bousfield localization of the $Joyal$ model structure, via Lurie's stratified singular functor $\mathrm{Sing}_{s}$, linking to layered $\infty$-categories with invertible endomorphisms. The work also analyzes bifibrant objects, provides detection criteria, and relates to Quinn's homotopically stratified spaces, while clarifying the relationship to conically smooth stratified spaces. By transferring model structures from stratified simplicial sets to topological stratifications, it establishes a robust, general framework for presenting stratified homotopy types and connects classical geometric examples to their $\infty$-categorical counterparts through explicit adjunctions between stratified realization and stratified singularization.
Abstract
This article is concerned with three different homotopy theories of stratified spaces: The one defined by Douteau and Henriques, the one defined by Haine, and the one defined by Nand-Lal. One of the central questions concerning these theories has been how precisely they connect with geometric and topological examples of stratified spaces, such as piecewise linear pseudomanifolds, Whitney stratified spaces, or more recently Ayala, Francis and Tanaka's conically smooth stratified spaces. More precisely, so far, it has been an open question whether there exist (semi-)model structures on stratified topological spaces that present these theories, in which such relevant examples of stratified spaces are bifibrant. Here, we prove an affirmative answer to this question. As a consequence, we obtain a model categorical interpretation of a stratified homotopy hypothesis. Specifically, we show that Lurie's stratified singular simplicial set functor induces a Quillen equivalence between the semimodel category of stratified topological spaces presenting Nand-Lal's homotopy theory of stratified spaces and the left Bousfield localization of the Joyal model structure that corresponds to such $\infty$-categories in which every endomorphism is an isomorphism. We then perform a detailed investigation of bifibrant objects in these model structures of stratified spaces, proving a series of detection criteria and illuminating the relationship to Quinn's homotopically stratified spaces.