Weight system
= Weight system
The weight system of a finite-dimensional <Lie algebra representation> is its collection of <weights> with their <weight multiplicities>. Restriction to a <Lie subalgebra> projects each <weight> to the smaller <Cartan subalgebra>, retaining and combining <weight multiplicities>. Grouping the resulting <weights> into irreducible <weight systems> computes the <branching rule>.