FLOC 2018: FEDERATED LOGIC CONFERENCE 2018
Internal Universes in Models of Homotopy Type Theory

Authors: Daniel R. Licata, Ian Orton, Andrew M. Pitts and Bas Spitters

Paper Information

Title:Internal Universes in Models of Homotopy Type Theory
Authors:Daniel R. Licata, Ian Orton, Andrew M. Pitts and Bas Spitters
Proceedings:FSCD Presented Papers
Editor: Helene Kirchner
Keywords:cubical sets, dependent type theory, homotopy type theory, internal language, modalities, univalent foundations, universes
Abstract:

ABSTRACT. We show that universes of fibrations in various models of homotopy type theory have an essentially global character: they cannot be described in the internal language of the presheaf topos from which the model is constructed. We get around this problem by extending the internal language with a modal operator for expressing properties of global elements. In this setting we show how to construct a universe that classifies the Cohen-Coquand-Huber-Mörtberg (CCHM) notion of fibration from their cubical sets model, starting from the assumption that the interval is tiny - a property that the interval in cubical sets does indeed have. This leads to a completely internal development of models of homotopy type theory within what we call crisp type theory.

Pages:17
Talk:Jul 10 10:00 (Session 52B: Types)
Paper: