  A homological invariant of 3-manifolds is defined, using abelian Yang-Mills
gauge theory. It is shown that the construction, in an appropriate sense, is
functorial with respect to the families of 4-dimensional cobordisms. This
construction and its functoriality are used to define several link invariants.
The strongest version of these invariants has the form of a filtered chain
complex that can recover Khovanov homology of the mirror image as a bi-graded
group.
