If there are multiple branes in the universe, in particular the two boundary branes in the ekpyrotic model, can the compactified dimensions in the two branes differ? The paper From Big Bang to Big Crunch by Khoury, Ovrut, Seiberg, Steinhardt and Turok (http://xxx.lanl.gov/PS_cache/hep-th/...08/0108187.pdf) seems to allow for the set of compactified dimensions to change in a collision between the end branes, but would the resulting metric in both end branes be identical?