Local right biadjoints, bistable pseudofunctors and 2-geometries for Grothendieck topoi

TL;DR

This paper develops bicategorical analogs of geometric notions in spectrum theory, introducing local right biadjoints and bistable pseudofunctors, and applies these to construct new factorization theorems for geometric morphisms in Grothendieck topoi.

Contribution

It introduces the concepts of local right biadjoints and bistable pseudofunctors, establishing their equivalence and applying them to develop new geometric factorization theorems.

Findings

Established equivalence between local right biadjoints and bistable pseudofunctors.

Described 2-dimensional orthogonality and factorization systems.

Proved a new factorization theorem for geometric morphisms in Grothendieck topoi.

Abstract

We provide bicategorical analogs of several aspects of the notion of geometry in the sense of the theory of spectrum. We first introduce a notion of local right biadjoint, and prove it to be equivalent to a notion of bistable pseudofunctor, categorifying an analog 1-categorical result. We also describe further laxness conditions, giving some properties of the already known lax familial pseudofunctors. We also describe 2-dimensional analogs of orthogonality and factorization systems, and use them to construct examples of bistable pseudofunctors through inclusion of left objects and left maps. We apply the latter construction to several examples of factorization systems for geometric morphisms to produce geometry-like situations for Grothendieck topoi. In particular we prove a new (terminally connected, pro-etale) factorization theorem for geometric morphisms, which corresponds to a certain local geometry involved in the general construction of spectra.