The ð ¶ -Version Segal-Bargmann Transform for Finite Coxeter Groups Defined by the Restriction Principle

We apply a special case, the restriction principle (for which we give a definition simpler than the usual one), of a basic result in functional analysis (the polar decomposition of an operator) in order to define ð ¶ ð œ‡ , ð ‘¡ , the ð ¶ -version of the Segal-Bargmann transform, associated with a finite Coxeter group acting in â„ ð ‘ and a given value ð ‘¡ > 0 of Planck's constant, where 𠜇 is a multiplicity function on the roots defining the Coxeter group. Then we immediately prove that ð ¶ ð œ‡ , ð ‘¡ is a unitary isomorphism. To accomplish this we identify the reproducing kernel function of the appropriate Hilbert space of holomorphic functions. As a consequence we prove that the Segal-Bargmann transforms for Versions ð ´ , ð µ , and ð · are also unitary isomorphisms though not by a direct application of the restriction principle. The point is that the ð ¶ -version is the only version where a restriction principle, in our definition of this method, applies directly. This reinforces the idea that the ð ¶ -version is the most fundamental, most natural version of the Segal-Bargmann transform.