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Operator algebras: subfactors and their applications

Participation in INI programmes is by invitation only. Anyone wishing to apply to participate in the associated workshop(s) should use the relevant workshop application form.

9th January 2017 to 23rd June 2017
David Evans Cardiff University
Masaki Izumi Kyoto University
Vaughan Jones Vanderbilt University, University of California, Berkeley, University of Auckland

The study of subfactors was initiated by Vaughan Jones in the early 1980's, in the theory of von Neumann algebras of operators on Hilbert spaces. Subfactor theory rapidly led to connections with link and 3-manifold invariants, quantum groups and exactly solvable models in statistical mechanics reinforcing the connections with physics. Subsequently deep applications and connections have been uncovered with algebraic, topological and conformal quantum field theory, with rapid progress in recent years in these applications. Free probability and planar algebra techniques have been combined to not only construct subfactors but derive matrix model computations in loop models of statistical mechanics.

These developments have led to connections between subfactors, non-commutative geometry and conformal field theory. In particular relationships between conformal nets of factors, twisted equivariant K-theory, K-homology, KK-theory, fusion and module categories and vertex operator algebras. The K-theoretic aspect of the programme includes higher twists as higher Dixmier-Douady twists and the categorification or higher geometry fronts. The search for geometric description of elliptic cohomology has led to relations with conformal field theories and conformal nets.

The programme will focus on these wide ranging applications as well as the underlying structure theory of operator algebras and subfactors. The classification of subfactors of small index has made strides in the last few years, involving the newer planar algebra tools, including the complete classification of subfactors with index values in the interval [4,5] and significant progress between 5 to just beyond 6. However there are very few constructions of subfactors that do not rely on group or quantum group symmetries. The challenge is to understand and even construct these allegedly exotic subfactors in a natural way and realising modular tensor categories as conformal field theories with conformal nets of factors and vertex operator algebras. There is much recent evidence that the Haagerup subfactor for example yields a natural conformal field theory.

University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons