Let me elaborate a little bit. If we live on a brane (for this purpose it's easiest to picture the brane's as flat 2 dimensional sheets running next to eachother) then we will feel the gravity of a mass on a neighboring brane. This helps to explain why only a very small portion of the "matter" in our universe is matter that we can see and touch. This matter would be quite mysterious as the only way we would have of measuring it would be from it's gravitational pull on objects in our universe. This add's up with our observations, we have virtually no solid evidence for what "Dark Matter" or "Dark Energy" really are. The only reason we know that it is there is because we can observe the gravitational pull it exerts on galaxies on our brane.
Now I'm not a physics student (although the prospect of it is quite appealing [it would be nice to have a well educated foundation to help easily discard rubbish thoughts that come up in my mind]) so my speculations are to be taken as nothing more than that.
If we do indeed live on one of these brane's that raises some questions. Where did these brane's come from? I'll not even bother focusing on that since we would need some basic understanding of the characteristics of this "multiverse". It is key here when picturing this multiverse that we see the importance of it in the development of our own universe. Matter on one brane would be attracted to matter on other brane's, and galaxies would form as a result of the gravity from galaxies forming on another brane. It stands to reason that dark matter would exist almost exclusively around galaxies in our own universe. So we can then ask if this can be confirmed by observaton. As it turns out, in our attempts to see dark matter, we have seen a "cloud" of unexplained mass covering the entire galaxy and extending our a bit past galaxies.
Hopefully you're still following me (I tend to offer foggy explanations), and you are now thinking along the same lines as I am. The cloud could theoretically be explained as the gravity exerted from the large number of galaxies on other branes.
So from here I ask, what about black holes? Black holes would undoubtebly be strongly attracted to eachother. A "supermassive" black hole seems likely to be a result of the most concentrated area of mass in this multibrane galaxy formation. Black holes fall into eachothers immense gravitational pull, eventually forming a "trunk" or "central pillar" around which galaxies on all of these branes orbit.
This brings me to my current problem. Wouldn't these "pilllars" have an infinite mass? Clearly they do not, so why? It could be that eventually all of the matter in these galaxies will end up on the same point, and we just haven't gotten there yet. It could be that there is a finite number of brane worlds. Or it could be that for some reason we have yet to understand, the fundamental force of gravity can only be exerted accross a certain number of branes (this seems less likely but is worth consideration).
I think I need to go post my idea's on a physics forum so that my errors can be corrected because this is mostly a result of me letting my mind
Hopefully that