The University of Michigan Combinatorics Seminar
We will present a simple set of axioms for combinatorial objects
that provide models for "Weyl characters"--the characters of
representations of semisimple Lie groups/algebras, or more
generally for "Kac-Weyl" characters--the analogues for Kac-Moody
algebras. Given any set of objects fitting the axioms, it is
trivial to derive rules for computing weight multiplicity, tensor
product multiplicity, and branching (restriction) rules.