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Given an algebraic theory $\ct$, a homotopy $\ct$-algebra is a simplicial set where all equations from $\ct$ hold up to homotopy. All homotopy $\ct$-algebras form a homotopy variety. We give a characterization of homotopy varieties…

Category Theory · Mathematics 2007-05-23 J. Rosicky

In this text we expose basic cases of some fundamental ideas and methods of topology. Namely, of homotopy, degree, fundamental group, covering, Whitehead invariant, etc. This is done by considering the elementary example: closed polygonal…

History and Overview · Mathematics 2026-05-07 E. Alkin , O. Nikitenko , A. Skopenkov

We combine Homotopy Type Theory with axiomatic cohesion, expressing the latter internally with a version of "adjoint logic" in which the discretization and codiscretization modalities are characterized using a judgmental formalism of "crisp…

Category Theory · Mathematics 2017-04-26 Michael Shulman

The thesis presents the subject of synthetic topology, especially with relation to metric spaces. A model of synthetic topology is a categorical model in which objects possess an intrinsic topology in a suitable sense, and all morphisms are…

General Topology · Mathematics 2021-04-22 Davorin Lešnik

This is an introduction to the study of abstract homotopy theory by means of model categories and $(\infty,1)$-categories. The only prerequisites are very basic general topology and abstract algebra. None categorical background is needed.…

Algebraic Topology · Mathematics 2020-08-13 Yuri Ximenes Martins

One of the prime motivation for topology was Homotopy theory, which captures the general idea of a continuous transformation between two entities, which may be spaces or maps. In later decades, an algebraic formulation of topology was…

Category Theory · Mathematics 2025-11-24 Suddhasattwa Das

In homotopy type theory (HoTT), all constructions are necessarily stable under homotopy equivalence. This has shortcomings: for example, it is believed that it is impossible to define a type of semi-simplicial types. More generally, it is…

Logic in Computer Science · Computer Science 2016-11-01 Thorsten Altenkirch , Paolo Capriotti , Nicolai Kraus

Recently discovered domain-specific formal systems -- specifically homotopy type theory and simplicial type theory -- provide new perspectives on spaces and categories in a natively equivalence-invariant setting. In this note, we expose…

Category Theory · Mathematics 2025-10-20 Emily Riehl

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 extend Homotopy Type Theory with a novel modality that is simultaneously a monad and a comonad. Because this modality induces a non-trivial endomap on every type, it requires a more intricate judgemental structure than previous modal…

Category Theory · Mathematics 2021-02-09 Mitchell Riley , Eric Finster , Daniel R. Licata

Homotopy type theory is an interpretation of Martin-L\"of's constructive type theory into abstract homotopy theory. There results a link between constructive mathematics and algebraic topology, providing topological semantics for…

Logic · Mathematics 2023-03-31 Steve Awodey , Nicola Gambino , Kristina Sojakova

Recent discoveries have been made connecting abstract homotopy theory and the field of type theory from logic and theoretical computer science. This has given rise to a new field, which has been christened "homotopy type theory". In this…

Logic · Mathematics 2012-10-23 Álvaro Pelayo , Michael A. Warren

Homotopy type theory (HoTT) can be seen as a generalisation of structural set theory, in the sense that 0-types represent structural sets within the more general notion of types. For material set theory, we also have concrete models as…

Logic · Mathematics 2025-10-31 Håkon Robbestad Gylterud , Elisabeth Stenholm

We investigate inductive types in type theory, using the insights provided by homotopy type theory and univalent foundations of mathematics. We do so by introducing the new notion of a homotopy-initial algebra. This notion is defined by a…

Logic · Mathematics 2015-04-22 Steve Awodey , Nicola Gambino , Kristina Sojakova

A type theory is presented that combines (intuitionistic) linear types with type dependency, thus properly generalising both intuitionistic dependent type theory and full linear logic. A syntax and complete categorical semantics are…

Logic in Computer Science · Computer Science 2026-05-07 Matthijs Vákár

The field of directed type theory seeks to design type theories capable of reasoning synthetically about (higher) categories, by generalizing the symmetric identity types of Martin-L\"of Type Theory to asymmetric hom-types. We articulate…

Category Theory · Mathematics 2025-10-21 Thorsten Altenkirch , Jacob Neumann

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

By introducing various topologies on the homotopy groups of a topological space, some researchers make these well known notions in algebraic topology more useful and powerful. In this paper, first we recall and review some known topologies…

Algebraic Topology · Mathematics 2026-02-25 Naghme Shahami , Behrooz Mashayekhy

Type theories can be formalized using the intrinsically (hard) or the extrinsically (soft) typed style. In large libraries of type theoretical features, often both styles are present, which can lead to code duplication and integration…

Logic in Computer Science · Computer Science 2021-07-19 Florian Rabe , Navid Roux