2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97659We consider the algebra associated to a group of transformations which are symmetries of a regular mechanical system (i.e. system free of constraints). For time dependent coordinate transformations we show that a central extension may appear at the classical level which is coordinate and momentum independent. A cochain formalism naturally arises in the argument and extends the usual configuration space cochain concepts to phase space.LaTeX, no figures, corrected for misprints, sent to Annals of Physics(NY)Quantum Physicstext