文摘
We define a family of associative products \({(\sharp_s)_{s>0}}\) on a space S ?/sub> of real analytic functions on \({\mathbb{C}^n}\) that are contained in the range of the heat transform for all times t?>?0. Extending results in Bauer (J Funct Anal 256:3107-142, 2009), Coburn (J Funct Anal 161:509-25, 1999; Proc Am Math Soc 129(11):3331-338, 2007) we show that this product leads to composition formulas of in general unbounded Berezin–Toeplitz operators \({T^{(s)}_f}\) on \({H_s^2}\) having symbols \({f \in S_{\infty}}\) . Here \({H_s^2}\) denotes the Segal–Bargmann space over \({\mathbb{C}^n}\) with respect to the semi-classical parameter s?>?0. In the special case of operators with polynomial symbols or for products of just two operators such formulas previously have been obtained in Bauer (J Funct Anal 256:3107-142, 2009), Coburn (Proc Am Math Soc 129(11):3331-338, 2007), respectively. Finally we give an example of a bounded real analytic function h on \({\mathbb{C}}\) such that \({(T_h^{(1)})^2}\) cannot be expressed in form of a Toeplitz operator \({T_g^{(1)}}\) where g fulfills a certain growth condition at infinity.