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Homotopy Type Theory is a new field of mathematics based on the surprising and elegant correspondence between Martin-Lofs constructive type theory and abstract homotopy theory. We have a powerful interplay between these disciplines - we can…

Logic in Computer Science · Computer Science 2014-02-10 Kristina Sojakova

This is an introductory textbook to univalent mathematics and homotopy type theory, a mathematical foundation that takes advantage of the structural nature of mathematical definitions and constructions. It is common in mathematical practice…

Logic · Mathematics 2022-12-22 Egbert Rijke

This paper discusses the development of synthetic cohomology in Homotopy Type Theory (HoTT), as well as its computer formalisation. The objectives of this paper are (1) to generalise previous work on integral cohomology in HoTT by the…

Algebraic Topology · Mathematics 2025-07-16 Axel Ljungström , Anders Mörtberg

Higher-dimensional rewriting systems are tools to analyse the structure of formally reducing terms to normal forms, as well as comparing the different reduction paths that lead to those normal forms. This higher structure can be captured by…

Logic in Computer Science · Computer Science 2023-02-15 Nicolai Kraus , Jakob von Raumer

Homotopy type theory is a formal language for doing abstract homotopy theory -- the study of identifications. But in unmodified homotopy type theory, there is no way to say that these identifications come from identifying the path-connected…

Category Theory · Mathematics 2022-04-06 David Jaz Myers

This note extends Quillen's Theorem A to a large class of categories internal to topological spaces. This allows us to show that under a mild condition a fully faithful and essentially surjective functor between such topological categories…

Algebraic Topology · Mathematics 2024-06-12 David Michael Roberts

This paper defines homology in homotopy type theory, in the process stable homotopy groups are also defined. Previous research in synthetic homotopy theory is relied on, in particular the definition of cohomology. This work lays the…

Logic · Mathematics 2018-12-27 Robert Graham

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

We use homotopy theory to extend the notion of strong and weak topological insulators to the non-stable regime (low numbers of occupied/empty energy bands). We show that for strong topological insulators in d spatial dimensions to be "truly…

Other Condensed Matter · Physics 2015-07-01 Ricardo Kennedy , Charles Guggenheim

We report on the development of the HoTT library, a formalization of homotopy type theory in the Coq proof assistant. It formalizes most of basic homotopy type theory, including univalence, higher inductive types, and significant amounts of…

Logic in Computer Science · Computer Science 2017-05-02 Andrej Bauer , Jason Gross , Peter LeFanu Lumsdaine , Mike Shulman , Matthieu Sozeau , Bas Spitters

Dynamic HoTT (DHoTT) is a conservative extension of Homotopy Type Theory designed for evolving texts in conversational AI. In a chat system, a large language model (LLM) is queried with a growing prefix: at turn tau the input is C(tau), the…

Logic in Computer Science · Computer Science 2025-11-18 Iman Poernomo

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

This paper introduces Isabelle/HoTT, the first development of homotopy type theory in the Isabelle proof assistant. Building on earlier work by Paulson, I use Isabelle's existing logical framework infrastructure to implement essential…

Logic in Computer Science · Computer Science 2021-04-20 Joshua Chen

In this paper we construct new categorical models for the identity types of Martin-L\"of type theory, in the categories Top of topological spaces and SSet of simplicial sets. We do so building on earlier work of Awodey and Warren, which has…

Logic · Mathematics 2011-10-17 Benno van den Berg , Richard Garner

Many introductions to homotopy type theory and the univalence axiom gloss over the semantics of this new formal system in traditional set-based foundations. This expository article, written as lecture notes to accompany a 3-part mini course…

Category Theory · Mathematics 2024-03-04 Emily Riehl

Voevodsky's univalence axiom is often motivated as a realization of the equivalence principle; the idea that equivalent mathematical structures satisfy the same properties. Indeed, in Homotopy Type Theory, properties and structures can be…

Logic in Computer Science · Computer Science 2022-11-15 Rafaël Bocquet

We present a development of the theory of higher groups, including infinity groups and connective spectra, in homotopy type theory. An infinity group is simply the loops in a pointed, connected type, where the group structure comes from the…

Logic in Computer Science · Computer Science 2018-02-14 Ulrik Buchholtz , Floris van Doorn , Egbert Rijke

Category theory in homotopy type theory is intricate as categorical laws can only be stated "up to homotopy", and thus require coherences. The established notion of a univalent category (Ahrens, Kapulkin, Shulman) solves this by considering…

Category Theory · Mathematics 2017-10-31 Paolo Capriotti , Nicolai Kraus

We consider the problem of defining the integers in Homotopy Type Theory (HoTT). We can define the type of integers as signed natural numbers (i.e., using a coproduct), but its induction principle is very inconvenient to work with, since it…

Logic in Computer Science · Computer Science 2020-07-02 Thorsten Altenkirch , Luis Scoccola

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