“…In general, the G-spin models with an Abelian group G, are known to have a symmetry group G × G, where G denotes the Pontryagin dual of G (the group of characters of G). If G is non-Abelian, the Pontryagin dual G loses its meaning and the models have a symmetry of a double algebra D(G) [14], which is an algebra defined as the crossed product of C(G) and CG with the adjoint action of the latter on the former ( [2], [5]). In detail, letting F be the field algebra of a G-spin model [14], there is a natural action of D(G) on F so that F becomes a D(G)-modular algebra.…”