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On a Model Invariance Problem in Homotopy Type Theory

Accepted version
Peer-reviewed

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Type

Article

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Authors

Bordg, Anthony Patrick 

Abstract

In this article, the author endows the functor category [B(Z/2Z),Gpd] with the structure of a type-theoretic fibration category with a univalent universe, using the so-called injective model structure. This gives a new model of Martin-Löf type theory with dependent sums, dependent products, identity types and a univalent universe. This model, together with the model (developed by the author in another work) in the same underlying category and with the same universe, which turns out to be provably not univalent with respect to projective fibrations, provide an example of two Quillen equivalent model categories that host different models of type theory. Thus, we provide a counterexample to the model invariance problem formulated by Michael Shulman.

Description

Keywords

4904 Pure Mathematics, 49 Mathematical Sciences

Journal Title

Applied Categorical Structures: a journal devoted to applications of categorical methods in algebra, analysis, order, topology and computer science

Conference Name

Journal ISSN

0927-2852
1572-9095

Volume Title

27

Publisher

Springer Nature
Sponsorship
European Research Council (742178)