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We study (not necessarily connected) Z-graded A-infinity-algebras and their A-infinity-modules. Using the cobar and the bar construction and Quillen's homotopical algebra, we describe the localisation of the category of A-infinity-algebras…

Category Theory · Mathematics 2007-05-23 Kenji Lefèvre-Hasegawa

We use the terms "$\infty$-categories" and "$\infty$-functors" to mean the objects and morphisms in an "$\infty$-cosmos." Quasi-categories, Segal categories, complete Segal spaces, naturally marked simplicial sets, iterated complete Segal…

Category Theory · Mathematics 2019-09-23 Emily Riehl , Dominic Verity

We give a new construction for rigidifying a quasi-category into a simplicial category, and prove that it is weakly equivalent to the rigidification given by Lurie. Our construction comes from the use of necklaces, which are simplicial sets…

Category Theory · Mathematics 2014-10-01 Daniel Dugger , David I. Spivak

We introduce a formalism based on a combinatorial notion of cell complex subject to an inclusion-reversing duality operation. Our main goal is to open the way for a functorial definition of field theories in a context where no manifold or…

Mathematical Physics · Physics 2022-04-15 Maxime Savoy

This paper gives a uniform-theoretic refinement of classical homotopy theory. Both cubical sets (with connections) and uniform spaces admit classes of weak equivalences, special cases of classical weak equivalences, appropriate for the…

Algebraic Topology · Mathematics 2021-09-20 Sanjeevi Krishnan , Crichton Ogle

The invertibility hypothesis for a monoidal model category S asks that localizing an S-enriched category with respect to an equivalence results in an weakly equivalent enriched category. This is the most technical among the axioms for S to…

Algebraic Topology · Mathematics 2016-02-18 Tyler Lawson

Consider a monoidal category which is at the same time abelian with enough projectives and such that projectives are flat on the right. We show that there is a $B_{\infty}$-algebra which is $A_{\infty}$-quasi-isomorphic to the derived…

K-Theory and Homology · Mathematics 2019-07-16 Wendy Lowen , Michel Van den Bergh

Given a recollement of three proper dg algebras over a noetherian commutative ring, e.g. three algebras which are finitely generated over the base ring, which extends one step downwards, it is shown that there is a short exact sequence of…

Representation Theory · Mathematics 2023-07-06 Haibo Jin , Dong Yang , Guodong Zhou

We present new data structures for quasistrict higher categories, in which associativity and unit laws hold strictly. Our approach has low axiomatic complexity compared to traditional algebraic definitions of higher categories, and we use…

Category Theory · Mathematics 2016-10-24 Krzysztof Bar , Jamie Vicary

In previous work, we introduce an axiomatic framework within which to prove theorems about many varieties of infinite-dimensional categories simultaneously. In this paper, we establish criteria implying that an $\infty$-category - for…

Category Theory · Mathematics 2020-07-17 Emily Riehl , Dominic Verity

Using a categorial version of Fra\"iss\'e's theorem due to Droste and G\"obel, we derive a criterion for a comma-category to have universal homogeneous objects. As a first application we give new existence result for universal structures…

Category Theory · Mathematics 2013-02-26 Christian Pech , Maja Pech

In this survey, we first present basic facts on A-infinity algebras and modules including their use in describing triangulated categories. Then we describe the Quillen model approach to A-infinity structures following K. Lefevre's thesis.…

Representation Theory · Mathematics 2007-05-23 Bernhard Keller

We prove that the K-theory of an exact quasicategory can be computed via a higher categorical variant of the Q construction. This construction yields a quasicategory whose weak homotopy type is a delooping of the K-theory space. We show…

K-Theory and Homology · Mathematics 2013-07-05 C. Barwick

We pursue the study of Ultracategories initiated by Makkai and more recently Lurie by looking at properties of Ultracategories of complete metric structures, i.e. coming from continuous model theory, instead of ultracategories of models of…

Category Theory · Mathematics 2026-04-06 Ali Hamad

We show that semi-infinite cohomology of a finite dimensional graded algebra (satisfying some additional requirements) are a particular case of a general categorical construction. The motivating example is provided by small quantum groups…

Representation Theory · Mathematics 2007-05-23 Roman Bezrukavnikov

Based on the algebraic cobordism theory of Levine and Morel, we develop a theory of algebraic cobordism modulo algebraic equivalence. We prove that this theory can reproduce Chow groups modulo algebraic equivalence and the semi-topological…

Algebraic Geometry · Mathematics 2012-09-10 Amalendu Krishna , Jinhyun Park

In this paper we redevelop the foundations of the category theory of quasi-categories (also called infinity-categories) using 2-category theory. We show that Joyal's strict 2-category of quasi-categories admits certain weak 2-limits, among…

Category Theory · Mathematics 2015-06-18 Emily Riehl , Dominic Verity

The unstraightening construction due to Lurie establishes an equivalence between presheaves and fibrations, using one prominent model of $(\infty,1)$-categories, namely quasi-categories. In this work we generalize this result by proving…

Category Theory · Mathematics 2025-06-06 Nima Rasekh

This article is a survey of algebra in the $\infty$-categorical context, as developed by Lurie in "Higher Algebra", and is a chapter in the "Handbook of Homotopy Theory". We begin by introducing symmetric monoidal stable…

Algebraic Topology · Mathematics 2019-07-08 David Gepner

A Q-system in a C* 2-category is a unitary version of a separable Frobenius algebra object and can be viewed as a unitary version of a higher idempotent. We define a higher unitary idempotent completion for C* 2-categories called Q-system…

Operator Algebras · Mathematics 2026-01-06 Quan Chen , Roberto Hernández Palomares , Corey Jones , David Penneys