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  • A Sequence to Compute the B...
    Cuadra, Juan; Femić, Bojana

    Applied categorical structures, 10/2012, Volume: 20, Issue: 5
    Journal Article

    A deeper understanding of recent computations of the Brauer group of Hopf algebras is attained by explaining why a direct product decomposition for this group holds and describing the non-interpreted factor occurring in it. For a Hopf algebra B in a braided monoidal category , and under certain assumptions on the braiding (fulfilled if is symmetric), we construct a sequence for the Brauer group of B -module algebras, generalizing Beattie’s one. It allows one to prove that , where is the Brauer group of and the group of B -Galois objects. We also show that contains a subgroup isomorphic to where is the second Sweedler cohomology group of B with values in the unit object I of . These results are applied to the Brauer group of a quasi-triangular Hopf algebra that is a Radford biproduct B × H , where H is a usual Hopf algebra over a field K , the Hopf subalgebra generated by the quasi-triangular structure is contained in H and B is a Hopf algebra in the category of left H -modules. The Hopf algebras whose Brauer group was recently computed fit this framework. We finally show that is a subgroup of , confirming the suspicion that a certain cohomology group of B × H (second lazy cohomology group was conjectured) embeds into it. New examples of Brauer groups of quasi-triangular Hopf algebras are computed using this sequence.