Using the Chern-Simon formulation of (2+1) gravity, we derive, for the
general asymptotic metrics given by the Fefferman-Graham-Lee theorems, the
emergence of the Liouville mode associated to the boundary degrees of freedom
of (2+1) dimensional anti de Sitter geometries.Comment: 6 pages, Latex, presented at the Journees Relativistes 99, Weimar,
September 12-17, 1999; revised version with minor modifications and 1
reference adde
