Existence and uniqueness of linking systems: Chermak's proof via 
obstruction theory

Bob Oliver

We present a version of a proof by Andy Chermak of the existence and 
uniqueness of centric linking systems associated to arbitrary saturated 
fusion systems.  This proof differs from the one by Chermak in that it is 
based on the computation of higher derived functors of certain inverse 
limits.  This leads to a much shorter proof, but one which is aimed mostly 
at researchers familiar with homological algebra.

Status:  submitted to Acta