**Definitions**

**Transfors between 2-categories**

**Morphisms in 2-categories**

**Structures in 2-categories**

**Limits in 2-categories**

**Structures on 2-categories**

The notion of *extensions* in a double category abstracts that of the classical operation of extension of scalars of bimodules. Indeed, they are usually available in framed bicategories, which are formal analogoues to double categories of bimodules; and indeed extensions in a double category of bimodules correspond to extensions of scalars.

The dual notion is that of **restriction**. Since having all restrictions is equivalent to having all extensions, and since in double category theory one usually works with the former, we redirect the reader to the aforementioned page.

- Mike Shulman,
*Framed bicategories and monoidal fibrations*, Theory and Applications of Categories**20**18 (2008) 650–738 [tac:2018, arXiv:0706.1286]

Last revised on August 14, 2024 at 12:04:37. See the history of this page for a list of all contributions to it.