Lifting bicategories through the Grothendieck construction

TL;DR

This paper develops a method to lift bicategories into double categories using the Grothendieck construction, enabling structured enhancements of bicategories with vertical morphisms and exploring their relations to various categorical structures.

Contribution

It introduces a novel approach to lift decorated bicategories into double categories via a specific Grothendieck construction, generalizing previous frameworks.

Findings

Every decorated bicategory admits a lift to a double category.

The construction relates to foldings, cofoldings, and framed bicategories.

Provides a systematic method for structured bicategory enhancement.

Abstract

We treat the problem of lifting bicategories into double categories through categories of vertical morphisms. We make use of a specific instance of the Grothendieck construction to provide, for every bicategory equipped with a possible vertical category, together with a suitable monoidal pre-cosheaf relating these two structures, a double category lifting the decorated bicategory along the category of vertical morphisms provided as set of initial conditions. We prove in particular that every decorated bicategory admits a lift to a double category. We study relations of instances of our construction to foldings, cofoldings, framed bicategories and globularily generated double categories.