Littelmann path model

Summary

The Littelmann path model is a combinatorial model of the finite-dimensional irreducible representations of a complex semisimple Lie algebra. It replaces the weights of a representation by piecewise linear paths that start at $0$ in the real span of the weights. Root operators act on these paths, and the endpoints of the paths reached from one dominant path give the weights with multiplicities. The model was introduced by Peter Littelmann and gives combinatorial rules for characters and tensor products.