  We have recently discovered a smooth vacuum-wormhole solution of the
first-order equations of general relativity. Here, we obtain the corresponding
multiple-vacuum-wormhole solution. Assuming that our world is essentially
Minkowski spacetime with a large number of these vacuum-defect wormholes
inserted, there is then another flat spacetime with opposite spatial
orientation, which may be called a "mirror" world. We briefly discuss some
phenomenological aspects and point out that there will be no significant
vacuum-Cherenkov radiation in our world, so that ultrahigh-energy cosmic rays
do not constrain the typical size and separation of the wormhole mouths
(different from the constraints obtained for a single Minkowski spacetime with
similar defects). Other signatures from a "gas" of vacuum-defect wormholes are
mentioned, including a possible time machine.
