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In this paper, we present a directed homotopy type theory for reasoning synthetically about (higher) categories, directed homotopy theory, and its applications to concurrency. We specify a new `homomorphism' type former for Martin-L\"of…

Logic in Computer Science · Computer Science 2018-07-30 Paige Randall North

As observed recently by various people the topos $\mathbf{sSet}$ of simplicial sets appears as essential subtopos of a topos $\mathbf{cSet}$ of cubical sets, namely presheaves over the category $\mathbf{FL}$ of finite lattices and monotone…

Category Theory · Mathematics 2021-03-15 Thomas Streicher , Jonathan Weinberger

We define a general class of dependent type theories, encompassing Martin-L\"of's intuitionistic type theories and variants and extensions. The primary aim is pragmatic: to unify and organise their study, allowing results and constructions…

Logic · Mathematics 2020-09-14 Andrej Bauer , Philipp G. Haselwarter , Peter LeFanu Lumsdaine

Since Quillen proved his famous equivalences of homotopy categories in 1969, much work has been done towards classifying the rational homotopy types of simply connected topological places. The majority of this work has focused on rational…

Algebraic Topology · Mathematics 2015-12-15 Matthew Zawodniak

In this note we remark on the problem of equality of objects in categories formalized in Martin-L\"of's constructive type theory. A standard notion of category in this system is E-category, where no such equality is specified. The main…

Category Theory · Mathematics 2019-09-17 Erik Palmgren

This is an expository introduction to simplicial sets and simplicial homotopy theory with particular focus on relating the combinatorial aspects of the theory to their geometric/topological origins. It is intended to be accessible to…

Algebraic Topology · Mathematics 2023-06-12 Greg Friedman

Nearness theory comes into play in homotopy theory because the notion of closeness between points is essential in determining whether two spaces are homotopy equivalent. While nearness theory and homotopy theory have different focuses and…

Algebraic Topology · Mathematics 2023-06-14 Melih Is , Ismet Karaca

We offer an introduction for mathematicians to the univalent foundations of Vladimir Voevodsky, aiming to explain how he chose to encode mathematics in type theory and how the encoding reveals a potentially viable foundation for all of…

Logic · Mathematics 2018-03-12 Daniel R. Grayson

The homotopical approach to intensional type theory views proofs of equality as paths. We explore what is required of an object $I$ in a topos to give such a path-based model of type theory in which paths are just functions with domain $I$.…

Logic in Computer Science · Computer Science 2023-06-22 Ian Orton , Andrew M. Pitts

We introduce the notion of a logical model category which is a Quillen model category satisfying some additional conditions. Those conditions provide enough expressive power that one can soundly interpret dependent products and sums in it.…

Logic · Mathematics 2012-08-30 Peter Arndt , Chris Kapulkin

The notion of a natural model of type theory is defined in terms of that of a representable natural transfomation of presheaves. It is shown that such models agree exactly with the concept of a category with families in the sense of Dybjer,…

Category Theory · Mathematics 2017-01-10 Steve Awodey

There have recently been several developments in synthetic mathematics using extensions of dependent type theory with univalence and higher inductive types: simplicial homotopy type theory, synthetic algebraic geometry and synthetic Stone…

Logic in Computer Science · Computer Science 2026-05-19 Thierry Coquand , Jonas Höfer , Christian Sattler

Using dependent type theory to formalise the syntax of dependent type theory is a very active topic of study and goes under the name of "type theory eating itself" or "type theory in type theory." Most approaches are at least loosely based…

Logic in Computer Science · Computer Science 2021-02-02 Nicolai Kraus

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

This is the fourth in a series of papers extending Martin-L\"of's meaning explanation of dependent type theory to higher-dimensional types. In this installment, we show how to define cubical type systems supporting a general schema of…

Logic in Computer Science · Computer Science 2018-07-20 Evan Cavallo , Robert Harper

It is a well-known theorem of homotopy type theory, originally due to Voevodsky, that function extensionality holds inside any univalent universe. We consider a weaker variant of the univalence axiom, asserting that the wild category formed…

Logic in Computer Science · Computer Science 2026-05-04 Evan Cavallo , Jonas Höfer

We discuss why Type Theory is preferable as foundation of Mathematics compared to set theory.

Logic · Mathematics 2023-01-10 Thorsten Altenkirch

We show that Martin Hyland's effective topos can be exhibited as the homotopy category of a path category $\mathbb{EFF}$. Path categories are categories of fibrant objects in the sense of Brown satisfying two additional properties and as…

Category Theory · Mathematics 2018-08-02 Benno van den Berg

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

In condensed matter physics and related areas, topological defects play important roles in phase transitions and critical phenomena. Homotopy theory facilitates the classification of such topological defects. After a pedagogic introduction…

Statistical Mechanics · Physics 2011-03-28 Ralph Kenna