  A region-delimited gravitational wave field can be constructed, such that a
subset of geodesics crossing this region will move faster than nearby geodesics
moving entirely inside flat spacetime, along a preferred direction. Null
geodesics inside this region will move faster-than-light according to far away
observers. The waveform is synthesized from homogeneous plane wave solutions,
and the resulting field is the gravitational equivalent of a Gaussian beam.
