http://xxx.lanl.gov/abs/hep-ph/9911386
The idea here is as follows:
This much is not original to the preprint above; it's a scenario that has been developed throughout the past year or so.
The new twist is:
3) The brane we inhabit is folded back on itself in the
extra dimensions. Electromagnetic and other 'gauge'
interactions are confined to the interior of the brane,
but gravity can travel through the 'bulk', the external
space in which the brane is embedded. The dark matter
whose gravitational influence we observe in astronomy is
just ordinary matter in a neighboring fold of the brane:
less than a millimeter away through the bulk, but perhaps
trillions of light-years away through the brane!