Coherent States of the q--Canonical Commutation Relations

For the $q$-deformed canonical commutation relations $a(f)a^\dagger(g) = (1-q)\,\langle f,g\rangle{\bf1}+q\,a^\dagger(g)a(f)$ for $f,g$ in some Hilbert space ${\cal H}$ we consider representations generated from a vector $Ω$ satisfying $a(f)Ω=\langle f,ϕ\rangleΩ$, where $ϕ\in{\cal H}$. We show that such a representation exists if and only if $\Vertϕ\Vert\leq1$. Moreover, for $\Vertϕ\Vert<1$ these representations are unitarily equivalent to the Fock representation (obtained for $ϕ=0$). On the other hand representations obtained for different unit vectors $ϕ$ are disjoint. We show that the universal C*-algebra for the relations has a largest proper, closed, two-sided ideal. The quotient by this ideal is a natural $q$-analogue of the Cuntz algebra (obtained for $q=0$). We discuss the Conjecture that, for $d<\infty$, this analogue should, in fact, be equal to the Cuntz algebra itself. In the limiting cases $q=\pm1$ we determine all irreducible representations of the relations, and characterize those which can be obtained via coherent states.

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