| Classical invariant theory is a field of study within abstract algebra that has been around for well over a century. However, the field of multiplicative invariant theory is rather new, having only been studied formally for the past 35 years. Multiplicative invariants arise naturally in a variety of settings, notably as representation rings of Lie algebras, centers of group algebras, and actions on algebraic tori. In this thesis we calculate the multiplicative invariants for lattices associated to root systems under the actions of their Weyl groups. |
