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Simplex category : ウィキペディア英語版 | Simplex category In mathematics, the simplex category (or simplicial category or nonempty finite ordinal category) is the category of non-empty finite ordinals and order preserving maps. It is used to define simplicial and cosimplicial objects. ==Formal definition==
The simplex category is usually denoted by . There are several equivalent descriptions of this category. can be described as the category of ''non-empty finite ordinals'' as objects, thought of as totally ordered sets, and ''order preserving functions'' as morphisms. The objects are commonly denoted (so that is the ordinal ). The category is generated by coface and codegeneracy maps, which amount to inserting or deleting elements of the orderings. (See simplicial set for relations of these maps.) A simplicial object is a presheaf on , that is a contravariant functor from to another category. For instance, simplicial sets are contravariant with the codomain category being the category of sets. A cosimplicial object is defined similarly as a covariant functor originating from .
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Simplex category」の詳細全文を読む
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