80 Complex reflection groups, cyclotomic algebras

Preliminary support for complex reflection groups and cyclotomic Hecke algebras has been added to the CHEVIE package. A complex reflection group is a group W acting on a vector space V, and generated by pseudo-reflections in V. The field of definition of W is defined to be the field of definition of V. It turns out that, as for rational reflection groups (Weyl groups), all representations of a complex reflection group W are defined over the field of definition of W (cf. Ben76 and D.~Bessis thesis). Similarly to Coxeter groups, complex reflection groups are represented by the permutation representation on a set of roots in V invariant by W and such that all reflections in W are reflections with respect to some root (see ComplexReflectionGroup). However there is no general theory on how to construct a nice set of roots for an arbitrary reflection group; the roots given in GAP where obtained case-by-case in an ad hoc way.

Irreducible complex reflection groups have been classified by Shephard and Todd. They contain one infinite family depending on 3 parameters, and 34 ``exceptional'' groups (which have been given by Shephard and Todd a number which actually varies from 4 to 37, and covers also the exceptional Coxeter groups, e.g., CoxeterGroup("E",8) is the group of Shephard-Todd number 37).

The cyclotomic Hecke algebra (see Hecke for complex reflection groups) corresponding to a complex reflection group is defined in a similar way as the Iwahori--Hecke algebra; for details see BM93. G.~Malle has computed character tables for some of these algebras, including all 2-dimensional groups, see BM93 and Mal96; CHEVIE contains those of type G(e,1,1), G_4, G_5, G_6, G_8, G_9, G_{12} and G_{25} in the Shephard-Todd classification.

Subsections

  1. ComplexReflectionGroup
  2. Operations for complex reflection groups
  3. Hecke for complex reflection groups
  4. Operations for cyclotomic Hecke algebras
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GAP 3.4.4
April 1997