Banach Journal of Mathematical Analysis

Cohomology for small categories: k-graphs and groupoids

Elizabeth Gillaspy and Alexander Kumjian

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Given a higher-rank graph Λ, we investigate the relationship between the cohomology of Λ and the cohomology of the associated groupoid GΛ. We define an exact functor between the Abelian category of right modules over a higher-rank graph Λ and the category of GΛ-sheaves, where GΛ is the path groupoid of Λ. We use this functor to construct compatible homomorphisms from both the cohomology of Λ with coefficients in a right Λ-module, and the continuous cocycle cohomology of GΛ with values in the corresponding GΛ-sheaf, into the sheaf cohomology of GΛ.


The current online version of this article, posted on 19 December 2017, supersedes the advance publication version posted on 10 November 2017. The affiliation and contact information for the first author have been corrected.

Article information

Banach J. Math. Anal., Volume 12, Number 3 (2018), 572-599.

Received: 9 February 2017
Accepted: 2 May 2017
First available in Project Euclid: 10 November 2017

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Mathematical Reviews number (MathSciNet)

Zentralblatt MATH identifier

Primary: 18B40: Groupoids, semigroupoids, semigroups, groups (viewed as categories) [See also 20Axx, 20L05, 20Mxx]
Secondary: 55N30: Sheaf cohomology [See also 18F20, 32C35, 32L10] 22E41: Continuous cohomology [See also 57R32, 57Txx, 58H10] 46L05: General theory of $C^*$-algebras

higher-rank graphs groupoids cohomology


Gillaspy, Elizabeth; Kumjian, Alexander. Cohomology for small categories: $k$ -graphs and groupoids. Banach J. Math. Anal. 12 (2018), no. 3, 572--599. doi:10.1215/17358787-2017-0041.

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