Reduced, tame, and exotic fusion systems

Kasper Andersen, Bob Oliver, Joana Ventura

Abstract:
We define here two new classes of saturated fusion systems, reduced fusion 
systems and tame fusion systems.  These are motivated by our attempts to 
better understand and search for exotic fusion systems:  fusion systems 
which are not the fusion systems of any finite group.  Our main theorems 
say that every saturated fusion system reduces to a reduced fusion system 
which is tame only if the original one is realizable, and that every 
reduced fusion system which is not tame is the reduction of some exotic 
(nonrealizable) fusion system.

(submitted, PLMS)