We introduce new modified Abelian lattice models, with inhomogeneous local
interactions, in which a sum over topological sectors are included in the
defining partition function. The dual models, on lattices with arbitrary
topology, are constructed and they are found to contain sums over topological
sectors, with modified groups, as in the original model. The role of the sum
over sectors is illuminated by deriving the field-strength formulation of the
models in an explicitly gauge-invariant manner. The field-strengths are found
to satisfy, in addition to the usual local Bianchi constraints, global
constraints. We demonstrate that the sum over sectors removes these global
constraints and consequently softens the quantization condition on the global
charges in the system. Duality is also used to construct mappings between the
order and disorder variables in the theory and its dual. A consequence of the
duality transformation is that correlators which wrap around non-trivial cycles
of the lattice vanish identically. For particular dimensions this mapping
allows an explicit expression for arbitrary correlators to be obtained.Comment: LaTeX 30 pages, 6 figures and 2 tables. References updated and
connection with earlier work clarified, final version to appear in Nucl.
Phys.