Looking for the universal covering of the smooth non-commutative torus leads to a curve of associative multiplications on the space $\\Cal O_M\'(\\Bbb R^{2n})\\cong \\Cal O_C(\\Bbb R^{2n})$ of Laurent Schwartz which is smooth in the deformation parameter $\\hbar$. The Taylor expansion in $\\hbar$ leads to the formal Moyal star product. The non-commutative torus and this version of the Heisenberg plane are examples of smooth *-algebras: smooth in the sense of having many derivations. A tentative definition of this concept is given.
@article{hal-00013424,
author = {Dubois-Violette, Michel and Kriegl, Andreas and Maeda, Yoshiaki and Michor, Peter W.},
title = {Smooth *-algebras},
journal = {HAL},
volume = {2001},
number = {0},
year = {2001},
language = {en},
url = {http://dml.mathdoc.fr/item/hal-00013424}
}
Dubois-Violette, Michel; Kriegl, Andreas; Maeda, Yoshiaki; Michor, Peter W. Smooth *-algebras. HAL, Tome 2001 (2001) no. 0, . http://gdmltest.u-ga.fr/item/hal-00013424/