Accessibility and presentability in 2-categories

Infinite Presentability of Groups and Condensation

We describe various classes of infinitely presented groups that are condensation points in the space of marked groups. A well-known class of such groups consists of finitely generated groups admitting an infinite minimal presentation. We introduce here a larger class of condensation groups, called infinitely independently presentable groups, and establish criteria which allow one to infer that ...

The 2-categories of G-categories and of G-graded Categories Are 2-equivalent

Given a group G, we prove that the 2-category of small categories with G-action and G-equivariant functors is 2-equivalent to the 2-category of small Ggraded categories and degree-preserving functors.

On Mass Problems of Presentability

We consider the notion of mass problem of presentability for countable structures, and study the relationship between Medvedev and Muchnik reducibilities on such problems and possible ways of syntactically characterizing these reducibilities. Also, we consider the notions of strong and weak presentability dimension and characterize classes of structures with presentability dimensions 1. 1 Basic...

Cohomology Theory in 2-categories

Recently, symmetric categorical groups are used for the study of the Brauer groups of symmetric monoidal categories. As a part of these efforts, some algebraic structures of the 2-category of symmetric categorical groups SCG are being investigated. In this paper, we consider a 2-categorical analogue of an abelian category, in such a way that it contains SCG as an example. As a main theorem, we ...

2-Categories and Yoneda lemma