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The treatment of equality as a type in type theory gives rise to an interesting type-theoretic structure known as `identity type'. The idea is that, given terms $a,b$ of a type $A$, one may form the type $Id_{A}(a,b)$, whose elements are…

Logic in Computer Science · Computer Science 2018-03-06 Arthur F. Ramos , Ruy J. G. B. de Queiroz , Anjolina G. de Oliveira , Tiago Mendonça Lucena de Veras

We will give a detailed account of why the simplicial sets model of the univalence axiom due to Voevodsky also models W-types. In addition, we will discuss W-types in categories of simplicial presheaves and an application to models of set…

Category Theory · Mathematics 2015-11-26 Benno van den Berg , Ieke Moerdijk

Simplicial type theory extends homotopy type theory with a directed path type which internalizes the notion of a homomorphism within a type. This concept has significant applications both within mathematics -- where it allows for synthetic…

Logic in Computer Science · Computer Science 2026-01-16 Daniel Gratzer , Jonathan Weinberger , Ulrik Buchholtz

The goal of this paper is to prove an equivalence between the model categorical approach to pro-categories, as studied by Isaksen, Schlank and the first author, and the $\infty$-categorical approach, as developed by Lurie. Three…

Algebraic Topology · Mathematics 2017-02-01 Ilan Barnea , Yonatan Harpaz , Geoffroy Horel

We introduce and compare two approaches to equivariant homotopy theory in a topological or ordinary Quillen model category. For the topological model category of spaces, we generalize Piacenza's result that the categories of topological…

Algebraic Topology · Mathematics 2017-03-06 Marc Stephan

$\infty$-category theory was originally developed in the context of classical homotopy theory using standard set theoretical assumptions, but has since been extended to a variety of mathematical foundations. One such successful effort,…

Category Theory · Mathematics 2025-08-13 Nima Rasekh

In this article, we construct a cofibrantly generated model structure on the category of spaces stratified over a fixed poset, and show that it is Quillen-equivalent to a category of diagrams of simplicial sets. Then, considering all those…

Algebraic Topology · Mathematics 2021-03-10 Sylvain Douteau

The usual homogeneous form of equality type in Martin-L\"of Type Theory contains identifications between elements of the same type. By contrast, the heterogeneous form of equality contains identifications between elements of possibly…

Logic in Computer Science · Computer Science 2022-03-15 Andrew M. Pitts

We prove a conjecture about the constructibility of coinductive types - in the principled form of indexed M-types - in Homotopy Type Theory. The conjecture says that in the presence of inductive types, coinductive types are derivable.…

Logic in Computer Science · Computer Science 2019-07-16 Benedikt Ahrens , Paolo Capriotti , Régis Spadotti

We introduce the notion of a "category with path objects", as a slight strengthening of Kenneth Brown's classic notion of a "category of fibrant objects". We develop the basic properties of such a category and its associated homotopy…

Category Theory · Mathematics 2017-06-21 Benno van den Berg , Ieke Moerdijk

Cubical type theory is an extension of Martin-L\"of type theory recently proposed by Cohen, Coquand, M\"ortberg and the author which allows for direct manipulation of $n$-dimensional cubes and where Voevodsky's Univalence Axiom is provable.…

Logic in Computer Science · Computer Science 2017-10-31 Simon Huber

This PhD thesis deals with some new models of intensional type theory and the Univalence Axiom introduced by Vladimir Voevodsky. Our work takes place in the framework of the definitions of type-theoretic fibration categories (the notion of…

Category Theory · Mathematics 2016-04-13 Anthony Bordg

This paper presents a type theory in which it is possible to directly manipulate $n$-dimensional cubes (points, lines, squares, cubes, etc.) based on an interpretation of dependent type theory in a cubical set model. This enables new ways…

Logic in Computer Science · Computer Science 2016-11-14 Cyril Cohen , Thierry Coquand , Simon Huber , Anders Mörtberg

The treatment of equality as a type in type theory gives rise to an interesting type-theoretic structure known as `identity type'. The idea is that, given terms $a,b$ of a type $A$, one may form the type $Id_{A}(a,b)$, whose elements are…

Logic in Computer Science · Computer Science 2018-04-27 Arthur Freitas Ramos , Ruy J. G. B. de Queiroz , Anjolina G. de Oliveira

Univalence was first defined in the setting of homotopy type theory by Voevodsky, who also (along with Kapulkin and Lumsdaine) adapted it to a model categorical setting, which was subsequently generalized to locally Cartesian closed…

Category Theory · Mathematics 2021-03-31 Nima Rasekh

We construct a discrete model of the homotopy theory of $S^1$-spaces. We define a category $\sP$ with objects composed of a simplicial set and a cyclic set along with suitable compatibility data. $\sP$ inherits a model structure from the…

Algebraic Topology · Mathematics 2007-05-23 Andrew J. Blumberg

Homotopy Type Theory may be seen as an internal language for the $\infty$-category of weak $\infty$-groupoids which in particular models the univalence axiom. Voevodsky proposes this language for weak $\infty$-groupoids as a new foundation…

Category Theory · Mathematics 2019-02-20 Egbert Rijke , Bas Spitters

Cubical type theory provides a constructive justification to certain aspects of homotopy type theory such as Voevodsky's univalence axiom. This makes many extensionality principles, like function and propositional extensionality, directly…

Logic in Computer Science · Computer Science 2018-05-02 Thierry Coquand , Simon Huber , Anders Mörtberg

In this paper we propose an approach to homotopical algebra where the basic ingredient is a category with two classes of distinguished morphisms: strong and weak equivalences. These data determine the cofibrant objects by an extension…

Algebraic Topology · Mathematics 2008-09-18 F. Guillen Santos , V. Navarro , P. Pascual , Agusti Roig

2-Theories are a canonical way of describing categories with extra structure. 2-theory-morphisms are used when discussing how one structure can be replaced with another structure. This is central to categorical coherence theory. We place a…

Category Theory · Mathematics 2007-05-23 Noson S. Yanofsky