arXiv math/06102602006-10-08math.CTmath.ATmath.CO

The Euler characteristic of a category

Tom Leinster

备注：: 24 pages
发表信息：: Documenta Mathematica 13 (2008), 21-49

英文摘要：

The Euler characteristic of a finite category is defined and shown to be compatible with Euler characteristics of other types of object, including orbifolds. A formula for the cardinality of the colimit of a diagram of sets is proved, generalizing the classical inclusion-exclusion formula. Both rest on a generalization of Mobius-Rota inversion from posets to categories.

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