Room 318

Hypergroups and subfactors

V. S. Sunder

IMSc

This series of lectures is about something I did between 25 and
30 years ago. (The reason for these lectures now is the insistence of my last
Ph.D. student Keshab.) This work started with the observation that the
collection of irreducible `bifinite bimodules over a $II_1$ factor' possessed a
group-like structure we shall refer to as `integral hypergroups'. Subfactors
`of finite depth' give rise to such hypergroups; while some finite hypergroups
give rise to subfactors of finite index. The first assertion above was proved
in the third of those three papers, while the second assertion was the content
of the first two.