Abelian categories are the most general category in which one can The idea and the name “abelian category” were first introduced by. In mathematics, an abelian category is a category in which morphisms and objects can be .. Peter Freyd, Abelian Categories; ^ Handbook of categorical algebra, vol. 2, F. Borceux. Buchsbaum, D. A. (), “Exact categories and duality”. BOOK REVIEWS. Abelian categories. An introduction to the theory of functors. By Peter. Freyd. (Harper’s Series in Modern Mathematics.) Harper & Row.

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There are numerous types of full, additive subcategories of abelian categories that occur in nature, as well as some conflicting terminology. Popescu, Abelian categories with applications to rings and modulesLondon Math.

The exactness properties of abelian categories have many features in common with exactness properties of toposes or of pretoposes. This result can be found as Theorem 7. By the second formulation of the definitionin an abelian category. Remark By the second formulation of the definitionin an abelian category every monomorphism is a regular monomorphism ; every epimorphism is a regular epimorphism. But under suitable conditions this comes down to working subject to an embedding into Ab Absee the discussion at Embedding into Ab below.

Given any pair AB of objects in an abelian category, there is a special zero morphism from A to B. If A is completethen we can remove the requirement that G be finitely generated; most generally, we can form finitary enriched limits in A.

## Abelian category

This page was last edited treyd 19 Marchat This exactness concept has been axiomatized in the theory of exact categoriesforming a very special case of regular categories. In an abelian category every morphism decomposes uniquely up to a unique isomorphism into the composition of an epimorphism and a monomorphismvia prop combined with def.

The category of sheaves of abelian groups on any site is abelian. See also the catlist discussion on comparison between abelian categories and topoi AT categories.

### abelian category in nLab

The class of Abelian categories is closed under several categorical constructions, for example, the category of chain complexes of an Abelian category, or the category of functors from a small category to an Abelian category are Abelian as well. In mathematicsan abelian category is a category in which morphisms and objects can be added and in which kernels and cokernels exist and have desirable properties. In fact, much of category theory was developed as a language to study these similarities.

The concept of abelian categories is one in a sequence of notions of additive catevories abelian categories. The following embedding theoremshowever, show that under good conditions an abelian category can be embedded into Ab as a full subcategory by an exact functorand generally can be embedded this way into R Mod R Modfor some ring R R. So 1 implies 2. The two were defined differently, but they had similar properties.

In an abelian category, every morphism f can be written as the composition of an epimorphism followed by a monomorphism.

Monographs 3Academic Press A discussion about to which extent abelian categories are a general context for homological algebra is archived at nForum here. From Wikipedia, the free categoriws. Abelian categories were introduced by Buchsbaum under the name abelisn “exact category” and Grothendieck in order to unify various cohomology theories. Going still further one should be able to obtain a nice theorem describing the image of the embedding of the weak 2-category of.

This epimorphism is called the coimage of fwhile the monomorphism is called the image of f. Proposition These two conditions are indeed fdeyd. All of the constructions used in that field are relevant, such as exact sequences, and especially short exact sequencesbaelian derived functors. The notion of abelian category is an abstraction of basic properties of the category Ab of abelian groupsmore generally of the category R R Mod of modules over some ringand still more generally of categories of sheaves of abelian groups and of modules.

Every monomorphism is a kernel and every epimorphism is a cokernel.

The essential image of I is a full, additive subcategory, but I is not exact. An abelian category is a pre-abelian category satisfying the following equivalent conditions.

Views Read Edit View history. Every abelian category A is a module over the monoidal category of finitely generated abelian groups; that is, we can form a tensor product of a finitely generated abelian group G and any object A of A. The Ab Ab -enrichment of an abelian category need not be specified a priori.