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Cleft Extensions of Hopf Algebroids

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An Erratum to this article was published on 25 October 2008

Abstract

The notions of a cleft extension and a cross product with a Hopf algebroid are introduced and studied. In particular it is shown that an extension (with a Hopf algebroid ℋ = (ℋ L , ℋ R )) is cleft if and only if it is ℋ R -Galois and has a normal basis property relative to the base ring L of ℋ L . Cleft extensions are identified as crossed products with invertible cocycles. The relationship between the equivalence classes of crossed products and gauge transformations is established. Strong connections in cleft extensions are classified and sufficient conditions are derived for the Chern–Galois characters to be independent on the choice of strong connections. The results concerning cleft extensions and crossed product are then extended to the case of weak cleft extensions of Hopf algebroids hereby defined.

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Authors and Affiliations

  1. Research Institute for Particle and Nuclear Physics, Budapest, 1525 Budapest 114, P.O.B. 49, Hungary

    Gabriella Böhm

  2. Department of Mathematics, University of Wales Swansea, Singleton Park, Swansea, SA2 8PP, UK

    Tomasz Brzeziński

Authors
  1. Gabriella Böhm
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  2. Tomasz Brzeziński
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Correspondence to Gabriella Böhm.

Additional information

Dedicated to Stef Caenepeel on the occasion of his 50th birthday.

An erratum to this article is available at http://dx.doi.org/10.1007/s10485-008-9168-x.

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Böhm, G., Brzeziński, T. Cleft Extensions of Hopf Algebroids. Appl Categor Struct 14, 431–469 (2006). https://doi.org/10.1007/s10485-006-9043-6

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  • DOI: https://doi.org/10.1007/s10485-006-9043-6

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