English

Partial Univalence in n-truncated Type Theory

Logic in Computer Science 2020-05-04 v1 Category Theory Logic

Abstract

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 question is then whether univalence restricted to h-propositions is compatible with UIP. We answer this affirmatively by constructing a model where types are elements of a closed universe defined as a higher inductive type in homotopy type theory. This universe has a path constructor for simultaneous "partial" univalent completion, i.e., restricted to h-propositions. More generally, we show that univalence restricted to (n1)(n-1)-types is consistent with the assumption that all types are nn-truncated. Moreover we parametrize our construction by a suitably well-behaved container, to abstract from a concrete choice of type formers for the universe.

Cite

@article{arxiv.2005.00260,
  title  = {Partial Univalence in n-truncated Type Theory},
  author = {Christian Sattler and Andrea Vezzosi},
  journal= {arXiv preprint arXiv:2005.00260},
  year   = {2020}
}

Comments

21 pages, long version of paper accepted at LICS 2020

R2 v1 2026-06-23T15:14:06.800Z