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The notion of Grothendieck topos may be considered as a generalisation of that of topological space, one in which the points of the space may have non-trivial automorphisms. However, the analogy is not precise, since in a topological space,…

Category Theory · Mathematics 2011-10-18 Richard Garner

We firstly introduce some key concepts in category theory, such as quotient category, completion of limits, $\mathrm{Mor}$ category, and so on; then give the concept of topology algebras and sheaves, and discuss how to restore the structue…

Category Theory · Mathematics 2019-06-11 Dezhao Zhang

We establish a unified group-theoretic framework bridging the arithmetic homotopy exact sequence of a variety and the Birman exact sequence of a surface. Within this framework, we reinterpret classical arithmetic notions - such as the…

Algebraic Geometry · Mathematics 2025-12-24 Miltiadis Karakikes , Sotiris Karanikolopoulos , Aristides Kontogeorgis , Dimitrios Noulas

In 1970s Segal outlined proofs of two theorems relating spaces of Fredholm and self-adjoint Fredholm operators with Quillen's constructions used to define higher algebraic K-theory. In the present paper we provide detailed proofs of these…

K-Theory and Homology · Mathematics 2023-02-09 Nikolai V. Ivanov

We introduce the notion of a geometric $(\infty,1)$-category, the protopyical example of which is an $(\infty,1)$-topos. We study (hyper)sheaves on geometric $(\infty,1)$-categories, proving that these are characterized by a form of…

Category Theory · Mathematics 2026-05-05 Connor Bass

In this paper, we address the construction of homotopy bicategories of $(\infty,2)$-categories, which we take as being modeled by 2-fold Segal spaces. Our main result is the concrete construction of a functor $h_2$ from the category of…

Category Theory · Mathematics 2025-02-14 Jack Romö

In this paper, we present a generalization of Grothendieck pretopologies -- suited for semicartesian categories with equalizers $C$ -- leading to a closed monoidal category of sheaves, instead of closed cartesian category. This is proved…

Category Theory · Mathematics 2024-04-19 Ana Luiza Tenório , Hugo Luiz Mariano

We define the notion of sheaf in the context of doctrines. We prove the associate sheaf functor theorem. We show that grothendieck toposes and toposes obtained by the tripos to topos construction are instances of categories of sheaves for a…

Logic · Mathematics 2014-09-05 Fabio Pasquali

Sigma models effectively describe ordered phases of systems with spontaneously broken symmetries. At low energies, field configurations fall into solitonic sectors, which are homotopically distinct classes of maps. Depending on context,…

Mathematical Physics · Physics 2018-11-01 J. P. Ang , Abhishodh Prakash

In this article, we interconnect two different aspects of higher category theory, in one hand the theory of infinity categories and on an other hand the theory of 2-categories.We construct an explicit functorial path objet in the model…

Algebraic Topology · Mathematics 2012-05-25 Ilias Amrani

This paper is a continuation of ``Operads, Grothendieck topologies and deformation theory'' (alg-geom/9502010). We show how to develop a cohomology theory that would control deformations of a sheaf of associative algebras over a scheme by…

alg-geom · Mathematics 2008-02-03 Dennis Gaitsgory

In this paper, we compare several functors which take simplicial categories or model categories to complete Segal spaces, which are particularly nice simplicial spaces which, like simplicial categories, can be considered to be models for…

Algebraic Topology · Mathematics 2007-10-11 Julia E. Bergner

In this work we shall introduce a new model structure on the category of pro-simplicial sheaves, which is very convenient for the study of \'etale homotopy. Using this model structure we define a pro-space associated to a topos, as a result…

Algebraic Topology · Mathematics 2015-12-03 Ilan Barnea , Tomer M. Schlank

This text develops a homotopy theory of 2-categories analogous to Grothendieck's homotopy theory of categories developed in "Pursuing Stacks". We define the notion of "basic localizer of 2-Cat", 2-categorical generalization of…

Algebraic Topology · Mathematics 2016-07-15 Jonathan Chiche

We formulate and prove a new variant of the Segal Conjecture describing the group of homotopy classes of stable maps from the p-completed classifying space of a finite group G to the classifying space of a compact Lie group K as the p-adic…

Algebraic Topology · Mathematics 2007-05-23 Kari Ragnarsson

J. Lurie proved in Higher Topos Theory that for $K$ a simplicial set, $\mathcal{C}$ a simplicial category, $f: \mathfrak{C}[K] \rightarrow \mathcal{C}^{\text{op}}$ an equivalence of simplicial categories, we have a Quillen equivalence…

Category Theory · Mathematics 2020-12-18 Renaud Gauthier

We define the notion of a model of higher-order modal logic in an arbitrary elementary topos $\mathcal{E}$. In contrast to the well-known interpretation of (non-modal) higher-order logic, the type of propositions is not interpreted by the…

Logic · Mathematics 2017-03-07 Steve Awodey , Kohei Kishida , Hans-Christoph Kotzsch

Digital topology is part of the ongoing endeavour to understand and analyze digitized images. With a view to supporting this endeavour, many notions from algebraic topology have been introduced into the setting of digital topology. But some…

Algebraic Topology · Mathematics 2019-05-21 Gregory Lupton , John Oprea , Nicholas Scoville

Many important theorems in differential topology relate properties of manifolds to properties of their underlying homotopy types -- defined e.g. using the total singular complex or the \v{C}ech nerve of a good open cover. Upon embedding the…

Algebraic Topology · Mathematics 2023-09-06 Adrian Clough

We investigate higher topological cyclic homology as an approach to studying chromatic phenomena in homotopy theory. Higher topological cyclic homology is constructed from the fixed points of a version of topological Hochschild homology…

Algebraic Topology · Mathematics 2013-04-30 Gunnar Carlsson , Christopher L. Douglas , Bjørn Ian Dundas