Frame transforms , star products and quantum mechanics on phase space

Using the notions of frame transform and of square integrable projective representation of a locally compact group G, we introduce a class of isometries (tight frame transforms) from the space of Hilbert-Schmidt operators in the carrier Hilbert space of the representation into the space of square integrable functions on the direct product group G × G. These transforms have remarkable properties; in particular, their ranges are reproducing kernel Hilbert spaces endowed with a suitable ‘star product’ which mimics, at the level of functions, the original product of operators. A ‘phase space formulation’ of quantum mechanics, by means of the transforms introduced in the present paper, and the link with the (generalized) Wigner transforms associated with square integrable representations are discussed.