New canonical structures in Liouville theories and strings without tachyons inD

Abstract
A general method is proposed within which one may systematically explore canonical structures in Liouville theories. By means of this method several regular as well as singular sectors of various Liouville theories are treated. In some of these canonical completeness is demonstrated. A heuristic canonical quantization within a modified string theory is then performed for the solved sectors of the Liouville theory. Some of the resulting open quantum strings turn out to be without tachyons for D.