  We present a local gluing construction for general relativistic initial data
sets. The method applies to generic initial data, in a sense which is made
precise. In particular the trace of the extrinsic curvature is not assumed to
be constant near the gluing points, which was the case for previous such
constructions. No global conditions on the initial data sets such as
compactness, completeness, or asymptotic conditions are imposed. As an
application, we prove existence of spatially compact, maximal globally
hyperbolic, vacuum space-times without any closed constant mean curvature
spacelike hypersurface.
