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Pushouts of Dwyer maps are $(\infty,1)$–categorical

Philip Hackney, Viktoriya Ozornova, Emily Riehl and Martina Rovelli

Algebraic & Geometric Topology 24 (2024) 2171–2183
Abstract

The inclusion of 1–categories into (,1)–categories fails to preserve colimits in general, and pushouts in particular. We observe that if one functor in a span of categories belongs to a certain previously identified class of functors, then the 1–categorical pushout is preserved under this inclusion. Dwyer maps, a kind of neighborhood deformation retract of categories, were used by Thomason in the construction of his model structure on 1–categories. Thomason previously observed that the nerves of such pushouts have the correct weak homotopy type. We refine this result and show that the weak homotopical equivalence is a weak categorical equivalence. We also identify a more general class of functors along which 1–categorical pushouts are (,1)–categorical.

Keywords
Dwyer map, nerve functor, $(\infty,1)$–category, simplicial category, quasicategory
Mathematical Subject Classification
Primary: 18N60, 55U35
References
Publication
Received: 3 June 2022
Revised: 8 March 2023
Accepted: 3 April 2023
Published: 16 July 2024
Authors
Philip Hackney
Department of Mathematics
University of Louisiana at Lafayette
Lafayette, LA
United States
Viktoriya Ozornova
Max Planck Institute for Mathematics
Bonn
Germany
Emily Riehl
Department of Mathematics
Johns Hopkins University
Baltimore, MD
United States
Martina Rovelli
Department of Mathematics and Statistics
University of Massachusetts at Amherst
Amherst, MA
United States

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