  Under suitable assumptions on the boundary conditions, it is shown that there
is a bijective correspondence between equivalence classes of asymptotic
reducibility parameters and asymptotically conserved n-2 forms in the context
of Lagrangian gauge theories. The asymptotic reducibility parameters can be
interpreted as asymptotic Killing vector fields of the background, with
asymptotic behaviour determined by a new dynamical condition. A universal
formula for asymptotically conserved n-2 forms in terms of the reducibility
parameters is derived. Sufficient conditions for finiteness of the charges
built out of the asymptotically conserved n-2 forms and for the existence of a
Lie algebra g among equivalence classes of asymptotic reducibility parameters
are given. The representation of g in terms of the charges may be centrally
extended. An explicit and covariant formula for the central charges is
constructed. They are shown to be 2-cocycles on the Lie algebra g. The general
considerations and formulas are applied to electrodynamics, Yang-Mills theory
and Einstein gravity.
