%0 Journal Article %T Generalised coherent states and the diagonal representation for operators %A N. Mukunda %A Arvind %A S. Chaturvedi %A R. Simon %J Physics %D 2000 %I arXiv %X We consider the problem of existence of the diagonal representation for operators in the space of a family of generalized coherent states associated with an unitary irreducible representation of a (compact) Lie group. We show that necessary and sufficient conditions for the possibility of such a representation can be obtained by combining Clebsch-Gordan theory and the reciprocity theorems associated with induced unitary group representation. Applications to several examples involving $SU(2),$ $SU(3),$ and the Heisenberg-Weyl group are presented, showing that there are simple examples of generalized coherent states which do not meet these conditions. Our results are relevant for phase-space description of quantum mechanics and quantum state reconstruction problems. %U http://arxiv.org/abs/quant-ph/0002070v1