It is natural to ask how far the
theory of closed invariant subspaces for Lp(G) can be extended to Birnbaum-Orlicz
spaces LA(G). If G is a compact group and A satisfles the Δ2− condition for
u ≧ u0≧ 0, the class of all closed invariant subspaces of LA(G) is exactly the family
{(LA)P: P ⊂ Σ} where Σ is the dual object of G. Distinct subsets of Σ engender
distinct subspaces.