Classification of problematic subgroups of U(n)
  We classify p-toral subgroups of U(n) that can have non-contractible fixed points under the action of U(n) on the complex of partitions of complex n-space into mutually orthogonal subspaces. 
Julia E. Bergner, Ruth Joachimi, Kathryn Lesh, Vesna Stojanoska,   Kirsten Wickelgren
math.AT