Andrew Slattery ; Jonathan Sterling - Hofmann-Streicher lifting of fibred categories

lmcs:17229 - Logical Methods in Computer Science, June 17, 2026, Volume 22, Issue 2 - https://doi.org/10.46298/lmcs-22(2:30)2026
Hofmann-Streicher lifting of fibred categoriesArticle

Authors: Andrew Slattery ; Jonathan Sterling

In 1997, Hofmann and Streicher introduced an explicit construction to lift a Grothendieck universe from the category of sets into the category of set-valued presheaves on a small category. More recently, Awodey presented an elegant functorial analysis of this construction in terms of the categorical nerve, the right adjoint to the functor that takes a presheaf to its category of elements; in particular, the categorical nerve's functorial action on the universal small discrete fibration gives the generic family of the universe's Hofmann-Streicher lifting. Inspired by Awodey's analysis, we define a relative version of Hofmann-Streicher lifting in terms of the right pseudo-adjoint to the 2-functor given by postcomposition with a fibration. Finally, we construct a new 2-bifibration of fibrations in which the opcartesian and cartesian lifts arise from these pseudo-adjunctions.


Volume: Volume 22, Issue 2
Secondary volumes: Selected Papers of the 39th and 40th ACM/IEEE Symposium on Logic in Computer Science (LICS 2024 and 2025)
Published on: June 17, 2026
Accepted on: April 22, 2026
Submitted on: January 6, 2026
Keywords: Category Theory, Logic in Computer Science

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