additive and abelian categories
(AB1) pre-abelian category
(AB2) abelian category
(AB5) Grothendieck category
left/right exact functor
With braiding
With duals for objects
category with duals (list of them)
dualizable object (what they have)
ribbon category, a.k.a. tortile category
With duals for morphisms
monoidal dagger-category?
With traces
Closed structure
Special sorts of products
Semisimplicity
Morphisms
Internal monoids
Examples
Theorems
In higher category theory
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
Ignacio López Franco has pointed 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. See:
Ignacio López Franco?, Tensor products of finitely cocomplete and abelian categories, Journal of Algebra 396, (2013) 207-219. (web)
Ignacio López Franco?, Tensor products of finitely cococomplete and abelian categories (2012) (pdf of slides)
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 March 21, 2024 at 21:42:19. See the history of this page for a list of all contributions to it.