Abstract
In this paper, we provide a notion of \(\infty \)-bicategories fibred in \(\infty \)-bicategories which we call 2-Cartesian fibrations. Our definition is formulated using the language of marked biscaled simplicial sets: Those are scaled simplicial sets equipped with an additional collection of triangles containing the scaled 2-simplices, which we call lean triangles, in addition to a collection of edges containing all degenerate 1-simplices. We prove the existence of a left proper combinatorial simplicial model category whose fibrant objects are precisely the 2-Cartesian fibrations over a chosen scaled simplicial set S. Over the terminal scaled simplicial set, this provides a new model structure modeling \(\infty \)-bicategories, which we show is Quillen equivalent to Lurie’s scaled simplicial set model. We conclude by providing a characterization of 2-Cartesian fibrations over an \(\infty \)-bicategory. This characterization then allows us to identify those 2-Cartesian fibrations arising as the coherent nerve of a fibration of \({\text {Set}}^+_{\Delta }\)-enriched categories, thus showing that our definition recovers the preexisting notions of fibred 2-categories.
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Note that this proposition is about the pushout-product of marked biscaled simplicial sets. For readability, we have omitted the marking and biscaling from the notation in the conclusion.
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Acknowledgements
We are grateful to an anonymous referee for the very careful reading which helped improve the article. F.A.G. would like to acknowledge the support of the VolkswagenStiftung through the Lichtenberg Professorship Programme while he conducted this research. W.H.S wishes to acknowledge the support of the NSF Research Training Group at the University of Virginia (grant number DMS-1839968) during the preparation of this work.
Funding
The first author acknowledges the support of the VolkswagenStiftung through the Lichtenberg Professorship Programme. The second author acknowledges the support of the NSF Research Training Group at the University of Virginia (Grant Number DMS-1839968) during the preparation of this work.
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Communicated by Nicola Gambino.
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Abellán García, F., Stern, W.H. 2-Cartesian Fibrations I: A Model for \(\infty \)-Bicategories Fibred in \(\infty \)-Bicategories. Appl Categor Struct 30, 1341–1392 (2022). https://doi.org/10.1007/s10485-022-09693-x
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DOI: https://doi.org/10.1007/s10485-022-09693-x