Shahn Majid

Bisections and cocycles on Hopf algebroids

We introduce and study the group \mathcal{B}(\mathcal{L}) of bisections of a Hopf algebroid \mathcal{L} and show that they form a group crossed module or 2 -group with the group \mathrm{Aut}(\mathcal{L}) of automorphisms. Moreover, the group of vertical bisections turns out to be...