Computations for Coxeter arrangements and Solomon's descent algebra:
Groups of rank three and four
Marcus Bishop,
J. Matthew Douglass,
Götz Pfeiffer,
and Gerhard Röhrle,
Abstract
In recent papers we have refined a conjecture of Lehrer and Solomon
expressing the character of the representation of a finite Coxeter group
W on the pth graded piece of its Orlik-Solomon algebra as a sum of
characters induced from linear characters of centralizers of elements of
W. Our refined conjecture relates the character of W on the pth
graded piece of its Orlik-Solomon algebra with the descent algebra of~W.
A consequence of our conjecture is that both the regular character of W
and the character of W acting on its Orlik-Solomon algebra have
parallel, graded decompositions as sums of characters induced from linear
characters of centralizers of elements of W, one for each conjugacy
class of elements of W.
The refined conjectures have been proved for symmetric and dihedral
groups. In this paper we develop algorithmic tools to prove the
conjectures computationally for a given W and we use these tools to
verify the claim for all finite Coxeter groups of rank three and four. The
techniques developed and implemented in this paper provide previously
unknown decompositions of the regular characters and the Orlik-Solomon
characters of the Coxeter groups of types B_3, H_3, B_4, D_4,
F_4, and H_4 as sums of induced representations indexed by the set of
conjugacy classes of W.
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