报告题目：Hopf-Galois Extensions and Twisted Hopf algebroids 

报告人：韩笑，Queen Mary University of London (伦敦玛丽女王大学)

时间：2023年1月31日（星期二）下午 14:30-16:00

腾讯会议：572-283-2445    会议密码：123456

摘要：We show that the Ehresmann-Schauenburg bialgebroid of a quantum principal bundle P or Hopf Galois extension with structure quantum group H is in fact a left Hopf algebroid \mathcal{L}(P,H). We look cleft extension of a certain `associative type' where \leftaction is an actual action. In this case also, we show that the associated left Hopf algebroid has an antipode obeying our minimal axioms. We show that if \mathcal{L} is any left Hopf algebroid then so is its cotwist \mathcal{L}^\varsigma as an extension of the previous bialgebroid Drinfeld cotwist theory.