Periodicity of irreducible modular and quantum characters

Abstract

For a root system R, a field K and an invertible element q in K let U be the associated quantum group, defined via Lusztig's divided powers construction. We study the irreducible characters of this algebra with integral (but not necessarily dominant) highest weight. If the l-th cyclotomic polynomial vanishes when evaluated at q, then these characters exhibit a certain l-periodicity.