Moment sets and unitary dual for the diamond group

Abstract

The diamond group G is a solvable group, semi-direct product of R with a ( 2 n + 1 )-dimensional Heisenberg group H n . We consider this group as a first example of a semi-direct product with the form R ⋉ N where N is nilpotent, connected and simply connected. Computing the moment sets for G, we prove that they separate the coadjoint orbits and its generic unitary irreducible representations. Then we look for the separation of all irreducible representations. First, moment sets separate representations for a quotient group G − of G by a discrete subgroup, then we can extend G to an overgroup G + , extend simultaneously each unitary irreducible representation of G to G + and separate the representations of G by moment sets for G + .