In attempting to come up with a semi-reasonable method of intergalactic travel, I ended up conceiving a general method of FTL travel relying on brane cosmology and the "bulk" being transversable in some way. More specifically, traveling from the brane through the bulk to another point on the brane acts like a highly non-linear map (in terms of distance traveled in the bulk's relationship to distance on the brane). The complexity involved in figuring out what path has to be transversed through the bulk to get to a specific point on the brane would make all but specifically mapped out routes too dangerous to attempt (sort of approximating a warp-gate network without actually having warp-gates).
My first question is whether or not this is at all compatible with actual theories of brane cosmology (this is really far from my area of expertise)? My second question is, assuming such travel is even theoretically possible, how much energy (order of magnitude) would be necessary to "breach" the bulk?
Having done additional research on the subject, it appears that the standard explanation for why additional dimensions are not apparent in brane cosmology is that material objects are the result of open strings and are "bound" to the brane on which our universe sits. As such, they cannot move orthogonally to the brane with which they are bound, which prevents them from interacting with the bulk (this also provides an explanation for the "weakness" of gravity; gravity is the result of closed string vibrations which are not bound to the brane and can leak out into the bulk). So, it seems that shifting from an open to closed string is necessary to interact with the bulk, which shifts the question to whether or not it is possible to have a string shift between open and closed states and if so how much energy does that require?