additive and abelian categories
(AB1) pre-abelian category
(AB2) abelian category
(AB5) Grothendieck category
left/right exact functor
category with duals (list of them)
dualizable object (what they have)
ribbon category, a.k.a. tortile category
monoidal dagger-category?
The natural tensor product operation on finite abelian categories is known as the Deligne tensor product or Deligne box product, introduced in (Deligne 90).
For $A$ and $B$ two abelian categories, their Deligne tensor product $A \boxtimes B$ is the abelian category such that for any other abelian category $C$ right exact functors of the form $A \boxtimes B \to C$ are equivalent to functors $A \times B \to C$ that are right exact in each argument separately.
This tensor product exists for finite abelian categories but not generally on all abelian categories. However a slight variant does: instead of abelian categories one can consider categories with finite colimits, see Franco 12 and (Chirvasitu&Johnson-Freyd 11, remark 2.2.8).
Recall that for every finite abelian category over $k$, there is a finite-dimensional algebra $A$ over $k$ and a $k$-linear equivalence of categories
where the right side consists of $A$-modules which are finite-dimensional as vector spaces over $k$. $A$ is uniquely determined up to Morita equivalence.
For $A, B \in Alg_k$ two finite-dimensional associative algebras over a field $k$, the Deligne tensor product of their categories of finite-dimensional modules is the category of finite-dimensional modules of the tensor product of algebras $A \otimes_k B$:
This appears for instance as (EGNO, prop. 1.46.2). Without the finiteness constraints and using the tensor product of categories with finite colimits, this appears as (Chirvasitu&Johnson-Freyd 11, remark 2.2.8).
The construction was introduced in
Festschrift, Vol. II. Progr. Math. 87, 111–195. Birkhäuser Boston. 1990 (1990)
A survey is in
Here the author points out that while Deligne’s tensor product always exists for finite abelian categories, it does not always exist for general abelian categories. He argues that in this case it is better to use Kelly’s tensor product of finitely cocomplete categories, because it always exists, and it agrees with Deligne’s tensor product when the latter exists.
Kelly’s tensor product can be found in section 6.5 of
Similar remarks (in the context of 2-rings/2-modules) are from corollary 2.2.5 on in
In this set of lecture notes
the Deligne tensor product is discussed in lecture 9.
Last revised on December 28, 2019 at 18:07:59. See the history of this page for a list of all contributions to it.