Contents
* Introduction
-- Why $S^1$-extended phase space?
-- Why central extensions of classical symmetries?
* Central extension \Gt of a group $G$
-- Group cohomology
-- Cohomology and contractions: Pseudo-cohomology
-- Principal bundle with connection $(\Gtm,\Theta)$
* Group Approach to Quantization
-- $U(1)$-quantization
-- Non-horizontal polarizations
* Simple examples
-- The abelian group $R^{k}$
-- The semisimple group $SU(2)$
* Algebraic anomalies
-- Higher-order polarizations
-- The Schr\"odinger group and Quantum Optics
-- The Virasoro group and String Theory