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We develop domain theory in constructive and predicative univalent foundations (also known as homotopy type theory). That we work predicatively means that we do not assume Voevodsky's propositional resizing axioms. Our work is constructive…

Logic in Computer Science · Computer Science 2023-09-29 Tom de Jong

A typoid is a type equipped with an equivalence relation, such that the terms of equivalence between the terms of the type satisfy certain conditions, with respect to a given equivalence relation between them, that generalise the properties…

Category Theory · Mathematics 2022-05-16 Iosif Petrakis

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

In this note we interpret Voevodsky's Univalence Axiom in the language of (abstract) model categories. We then show that any posetal locally Cartesian closed model category $Qt$ in which the mapping $Hom^{(w)}(Z\times B,C):Qt\longrightarrow…

Category Theory · Mathematics 2011-11-16 Misha Gavrilovich , Assaf Hasson , Itay Kaplan

We develop category theory within Univalent Foundations, which is a foundational system for mathematics based on a homotopical interpretation of dependent type theory. In this system, we propose a definition of "category" for which equality…

Category Theory · Mathematics 2019-02-20 Benedikt Ahrens , Chris Kapulkin , Michael Shulman

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

We present Voevodsky's construction of a model of univalent type theory in the category of simplicial sets. To this end, we first give a general technique for constructing categorical models of dependent type theory, using universes to…

Logic · Mathematics 2026-02-06 Chris Kapulkin , Peter LeFanu Lumsdaine

We prove the conjecture that any Grothendieck $(\infty,1)$-topos can be presented by a Quillen model category that interprets homotopy type theory with strict univalent universes. Thus, homotopy type theory can be used as a formal language…

Algebraic Topology · Mathematics 2019-04-30 Michael Shulman

We give a model of set theory based on multisets in homotopy type theory. The equality of the model is the identity type. The underlying type of iterative sets can be formulated in Martin-L\"of type theory, without Higher Inductive Types…

Logic · Mathematics 2020-07-08 Håkon Robbestad Gylterud

The study of homotopy theoretic phenomena in the language of type theory is sometimes loosely called `synthetic homotopy theory'. Homotopy theory in type theory is only one of the many aspects of homotopy type theory, which also includes…

Logic · Mathematics 2019-06-25 Egbert Rijke

We present a concept of uniform encodability of theories and develop tools related to this concept. As an application we obtain general undecidability results which are uniform for large families of structures. In the way, we define…

Logic · Mathematics 2010-12-07 Hector Pasten , Thanases Pheidas , Xavier Vidaux

We provide a formulation of the univalence axiom in a universe category model of dependent type theory that is convenient to verify in homotopy-theoretic settings. We further develop a strengthening of the univalence axiom, called pointed…

Logic in Computer Science · Computer Science 2025-12-19 Chris Kapulkin , Yufeng Li

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

It is well known that univalence is incompatible with uniqueness of identity proofs (UIP), the axiom that all types are h-sets. This is due to finite h-sets having non-trivial automorphisms as soon as they are not h-propositions. A natural…

Logic in Computer Science · Computer Science 2020-05-04 Christian Sattler , Andrea Vezzosi

In this paper, we analyze and compare three of the many algebraic structures that have been used for modeling dependent type theories: categories with families, split type-categories, and representable maps of presheaves. We study these in…

Logic · Mathematics 2023-06-22 Benedikt Ahrens , Peter LeFanu Lumsdaine , Vladimir Voevodsky

Category theory unifies mathematical concepts, aiding comparisons across structures by incorporating objects and morphisms, which capture their interactions. It has influenced areas of computer science such as automata theory, functional…

Category Theory · Mathematics 2024-02-09 Nima Rasekh , Niels van der Weide , Benedikt Ahrens , Paige Randall North

We generalise sheaf models of intuitionistic logic to univalent type theory over a small category with a Grothendieck topology. We use in a crucial way that we have constructive models of univalence, that can then be relativized to any…

Logic · Mathematics 2020-07-09 Thierry Coquand , Fabian Ruch , Christian Sattler

Algebraic theories with dependency between sorts form the structural core of Martin-L\"of type theory and similar systems. Their denotational semantics are typically studied using categorical techniques; many different categorical…

Category Theory · Mathematics 2024-12-31 Benedikt Ahrens , Peter LeFanu Lumsdaine , Paige Randall North

Connections between homotopy theory and type theory have recently attracted a lot of attention, with Voevodsky's univalent foundations and the interpretation of Martin-Lof's identity types in Quillen model categories as some of the…

Category Theory · Mathematics 2016-09-21 Benno van den Berg

We construct a new model category presenting the homotopy theory of presheaves on "inverse EI $(\infty,1)$-categories", which contains universe objects that satisfy Voevodsky's univalence axiom. In addition to diagrams on ordinary inverse…

Algebraic Topology · Mathematics 2017-03-30 Michael Shulman