Alladi Ramakrishnan Hall

Angle between intermediate subfactors.

Keshab Chandra Bakshi

CMI

We introduce a new notion of angle between intermediate
subfactors and show that it only takes values (strictly) between 60
and 90 degrees for minimal intermediate subfactors of a finite index
irreducible subfactor. From this rigidity we can bound the number of
minimal intermediate subfactors using an elementary estimate on
kissing numbers in geometry. As a consequence, we improve the existing
upper bound of the cardinality of the set of all intermediate subfactors
thereby answering a question of R. Longo published in 2003. This is joint
work with S. Das, Z. Liu and Y. Ren.