Subgroups of the Brauer group of a cocommutative coalgebra (Q1570890)

Let \(C\) be a coalgebra over the field \(k\) and \(\mathcal H\) a class of groups closed under finite products and opposites. The authors define the Schur subgroup and the projective Schur subgroup of the Brauer group of \(C\) and they study the properties of these subgroups. These two subgroups are torsion provided that \(k\) has characteristic zero, in contrast with the whole Brauer group. The connection with the subgroups associated to the coradical of \(C\) is investigated.