2008
DOI: 10.1016/j.aim.2008.07.014
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Hochschild and ordinary cohomology rings of small categories

Abstract: Let C be a small category and k a field. There are two interesting mathematical subjects: the category algebra kC and the classifying space |C| = BC. We study the ring homomorphism HH * (kC) → H * (|C|, k) and prove it is split surjective, using the factorization category of Quillen [18] and certain techniques from functor cohomology theory. This generalizes the well-known theorems for groups and posets. Based on this result, we construct a seven-dimensional category algebra whose Hochschild cohomology ring mo… Show more

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Cited by 55 publications
(56 citation statements)
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“…There are examples, due to Fei Xu [24], of finite categories for which not even the quotient of the Hochschild cohomology by its nil-radical is finitely generated. In contrast, for finite inverse categories, the above theorem has the following consequence: Corollary 1.2.…”
Section: Introductionmentioning
confidence: 99%
“…There are examples, due to Fei Xu [24], of finite categories for which not even the quotient of the Hochschild cohomology by its nil-radical is finitely generated. In contrast, for finite inverse categories, the above theorem has the following consequence: Corollary 1.2.…”
Section: Introductionmentioning
confidence: 99%
“…Note that F (P), identified with a subposet of P e , is convex but not ideal in P e kP⋊G . see [11] for the latter isomorphism. Along with Boisen's result, our first statement gives rise to the second.…”
Section: Block Theorymentioning
confidence: 93%
“…Enveloping categories and diagonal categories. These constructions were used in [11]. Let C e = C × C op be the product category, between a small category C and its opposite, called the enveloping category.…”
Section: 2mentioning
confidence: 99%
“…Moreover, [16,17], and [20] make us consider whether we can give necessary and sufficient conditions on a finite dimensional algebra A for HH * A / to be finitely generated as an algebra (cf. [14,Introduction]).…”
Section: Introductionmentioning
confidence: 99%