2014/03/19 by Hoge, Torsten, Roehrle, Gerhard
#14N20 #20F55 #52C35 #Combinatorics (math.CO) #Commutative Algebra (math.AC) #FOS: Mathematics #Group Theory (math.GR)
paper · doi:10.48550/arxiv.1403.4725
In 1989, Ziegler introduced the concept of a multi-arrangement. One natural example is the reflection arrangement of a unitary reflection group with multiplicity given by the number of reflections associated with each hyperplane. For all but three irreducible groups, Ziegler showed that each such multi-reflection arrangement is free. We complete Ziegler's example by confirming these outstanding cases.