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Examples of Sweedler cohomology in positive characteristic. (English) Zbl 1316.81056

Summary: There have been few examples of computations of Sweedler cohomology, or its generalization in low degrees known as lazy cohomology, for Hopf algebras of positive characteristic. In this paper we first provide a detailed calculation of the Sweedler cohomology of the algebra of functions on \((\mathbb{Z}/2)^r\), in all degrees, over a field of characteristic 2. Here the result is strikingly different from the characteristic zero analog.{ }Then we show that there is a variant in characteristic \(p\) of the result obtained by Kassel and the author in characteristic zero, which provides a near-complete calculation of the second lazy cohomology group in the case of function algebras over a finite group; in positive characteristic, the statement is, rather surprisingly, simpler.

MSC:

81R50 Quantum groups and related algebraic methods applied to problems in quantum theory
16T05 Hopf algebras and their applications
11F52 Modular forms associated to Drinfel’d modules
11F22 Relationship to Lie algebras and finite simple groups
20C33 Representations of finite groups of Lie type
20C35 Applications of group representations to physics and other areas of science

References:

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[4] DOI: 10.1006/jabr.1993.1102 · Zbl 0787.16028 · doi:10.1006/jabr.1993.1102
[5] DOI: 10.1090/S0002-9947-1968-0224684-2 · doi:10.1090/S0002-9947-1968-0224684-2
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