Morse flow categories as exit path categories

Fuente: arXiv
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Auteur principal: Fourel, Colin
Format: Preprint
Publié: 2026
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author Fourel, Colin
author_facet Fourel, Colin
contents We prove that the topological flow category $\mathcal{M}$ arising from a Morse-Smale pair $(f,ξ)$ on a smooth closed manifold $X$ is equivalent, as an $\infty$-category, to Lurie's $\infty$-category $\mathrm{Sing}_A(X)$ of exit paths in $X$ with respect to the stratification by the stable manifolds of $ξ$. The objects of $\mathcal{M}$ are the critical points of $f$, and for every pair of critical points, the space of morphisms of $\mathcal{M}$ between these is the space of possibly broken trajectories of $ξ$ connecting them; it can be identified up to homotopy with the space of unbroken ones. The latter maps naturally to the space of exit paths connecting these critical points; we prove this map to be a weak homotopy equivalence. Then, we combine these ingredients with several others to construct a zigzag of equivalences between the homotopy coherent nerve of $\mathcal{M}$, denoted $\mathcal{N}(\mathcal{M})$, and $\mathrm{Sing}_A(X)$. The $n$-simplices of $\mathcal{N}(\mathcal{M})$ are homotopy coherent diagrams of $n$ composable morphisms of $\mathcal{M}$; we introduce the notion of unbroken diagram, yielding an $\infty$-subcategory of $\mathcal{N}(\mathcal{M})$, which we refer to as the flow coherent nerve of $\mathcal{M}$. The simplices of the latter give rise to stratified maps out of a family of stratified cubes, into $X$. We organize this family into a functor from the category of finite ordered sequences of critical points, to the category of $A$-stratified topological spaces, and we prove a comparison result with the usual stratified geometric realization functor. We finally use a theorem of Tanaka that associates a functor of $\infty$-categories to a map a semi-simplicial sets satisfying some conditions. Our theorem has implications regarding constructible sheaves and the description of homotopy types in terms of flow categories.
format Preprint
id arxiv_https___arxiv_org_abs_2605_27112
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Morse flow categories as exit path categories
Fourel, Colin
Algebraic Topology
Category Theory
Symplectic Geometry
18N50, 18N60, 57R25, 58A35
We prove that the topological flow category $\mathcal{M}$ arising from a Morse-Smale pair $(f,ξ)$ on a smooth closed manifold $X$ is equivalent, as an $\infty$-category, to Lurie's $\infty$-category $\mathrm{Sing}_A(X)$ of exit paths in $X$ with respect to the stratification by the stable manifolds of $ξ$. The objects of $\mathcal{M}$ are the critical points of $f$, and for every pair of critical points, the space of morphisms of $\mathcal{M}$ between these is the space of possibly broken trajectories of $ξ$ connecting them; it can be identified up to homotopy with the space of unbroken ones. The latter maps naturally to the space of exit paths connecting these critical points; we prove this map to be a weak homotopy equivalence. Then, we combine these ingredients with several others to construct a zigzag of equivalences between the homotopy coherent nerve of $\mathcal{M}$, denoted $\mathcal{N}(\mathcal{M})$, and $\mathrm{Sing}_A(X)$. The $n$-simplices of $\mathcal{N}(\mathcal{M})$ are homotopy coherent diagrams of $n$ composable morphisms of $\mathcal{M}$; we introduce the notion of unbroken diagram, yielding an $\infty$-subcategory of $\mathcal{N}(\mathcal{M})$, which we refer to as the flow coherent nerve of $\mathcal{M}$. The simplices of the latter give rise to stratified maps out of a family of stratified cubes, into $X$. We organize this family into a functor from the category of finite ordered sequences of critical points, to the category of $A$-stratified topological spaces, and we prove a comparison result with the usual stratified geometric realization functor. We finally use a theorem of Tanaka that associates a functor of $\infty$-categories to a map a semi-simplicial sets satisfying some conditions. Our theorem has implications regarding constructible sheaves and the description of homotopy types in terms of flow categories.
title Morse flow categories as exit path categories
topic Algebraic Topology
Category Theory
Symplectic Geometry
18N50, 18N60, 57R25, 58A35
url https://arxiv.org/abs/2605.27112