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Cellini's descent algebra and semisimple conjugacy classes of finite groups of Lie type

Jason Fulman
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Abstract

By algebraic group theory, there is a map from the semisimple conjugacy classes of a finite group of Lie type to the conjugacy classes of the Weyl group. Picking a semisimple class uniformly at random yields a probability measure on conjugacy classes of the Weyl group. We conjecture that this measure agrees with a second measure on conjugacy classes of the Weyl group induced by a construction of Cellini which uses the affine Weyl group. This conjecture is confirmed in special cases such as type C odd characteristic and the identity conjugacy class in type A. Models of card shuffling, old and new, arise naturally. Type A shuffles lead to interesting number theory involving Ramanujan sums. It is shown that a proof of our conjecture in type C even characteristic would give an alternate solution to a problem in dynamical systems. An idea is offered for how, at least in type A, to associate to a semisimple conjugacy class an element of the Weyl group, refining the map to conjugacy classes. This is confirmed for the simplest nontrivial example.

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Jason Fulman. 2000-03-30. Cellini's descent algebra and semisimple conjugacy classes of finite groups of Lie type. https://arxiv.org/abs/math/9909121

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