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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

We build free, bigraded bidifferential algebra models for the forms on a complex manifold, with respect to a strong notion of quasi-isomorphism and compatible with the conjugation symmetry. This answers a question of Sullivan. The resulting…

Algebraic Topology · Mathematics 2024-11-27 Jonas Stelzig

Higher inductive types (HITs) in Homotopy Type Theory (HoTT) allow the definition of datatypes which have constructors for equalities over the defined type. HITs generalise quotient types and allow to define types which are not sets in the…

Logic in Computer Science · Computer Science 2018-05-09 Thorsten Altenkirch , Paolo Capriotti , Gabe Dijkstra , Nicolai Kraus , Fredrik Nordvall Forsberg

Semi-simplicial and semi-cubical sets are commonly defined as presheaves over respectively, the semi-simplex or semi-cube category. Homotopy Type Theory then popularized an alternative definition, where the set of n-simplices or n-cubes are…

Logic in Computer Science · Computer Science 2025-07-22 Hugo Herbelin , Ramkumar Ramachandra

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

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

We show that contrary to appearances, Multimodal Type Theory (MTT) over a 2-category M can be interpreted in any M-shaped diagram of categories having, and functors preserving, M-sized limits, without the need for extra left adjoints. This…

Category Theory · Mathematics 2024-02-14 Michael Shulman

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

We present a new model of Guarded Dependent Type Theory (GDTT), a type theory with guarded recursion and multiple clocks in which one can program with, and reason about coinductive types. Productivity of recursively defined coinductive…

Logic in Computer Science · Computer Science 2020-04-14 Aleš Bizjak , Rasmus Ejlers Møgelberg

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

Higher inductive types are a class of type-forming rules, introduced to provide basic (and not-so-basic) homotopy-theoretic constructions in a type-theoretic style. They have proven very fruitful for the "synthetic" development of homotopy…

Logic · Mathematics 2020-07-08 Peter LeFanu Lumsdaine , Mike Shulman

We explore a quantitative interpretation of 2-dimensional intuitionistic type theory (ITT) in which the identity type is interpreted as a "type of differences". We show that a fragment of ITT, that we call difference type theory (dTT),…

Logic in Computer Science · Computer Science 2021-07-14 Paolo Pistone

We propose foundations for a synthetic theory of $(\infty,1)$-categories within homotopy type theory. We axiomatize a directed interval type, then define higher simplices from it and use them to probe the internal categorical structures of…

Category Theory · Mathematics 2023-06-09 Emily Riehl , Michael Shulman

We show that certain diagrams of $\infty$-logoses are reconstructed in homotopy type theory extended with some lex, accessible modalities, which enables us to use plain homotopy type theory to reason about not only a single $\infty$-logos…

Category Theory · Mathematics 2026-03-18 Taichi Uemura

This paper is part of a series of papers about homotopy theory of strict $n$-categories. In the first paper of this series, we gave conditions that guarantee the existence of a Thomason model category structure on the category of strict…

Algebraic Topology · Mathematics 2015-03-11 Dimitri Ara , Georges Maltsiniotis

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

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

In this paper we combine the principled approach to modalities from multimodal type theory (MTT) with the computationally well-behaved realization of identity types from cubical type theory (CTT). The result -- cubical modal type theory…

Logic in Computer Science · Computer Science 2024-12-18 Frederik Lerbjerg Aagaard , Magnus Baunsgaard Kristensen , Daniel Gratzer , Lars Birkedal

Univalent homotopy type theory (HoTT) may be seen as a language for the category of $\infty$-groupoids. It is being developed as a new foundation for mathematics and as an internal language for (elementary) higher toposes. We develop the…

Category Theory · Mathematics 2023-06-22 Egbert Rijke , Michael Shulman , Bas Spitters

We introduce the notion of a template for discrete Morse theory. Templates provide a memory efficient approach to the computation of homological invariants (e.g., homology, persistent homology, Conley complexes) of cell complexes. We…

Algebraic Topology · Mathematics 2021-06-30 Shaun Harker , Konstantin Mischaikow , Kelly Spendlove