Can we live in the bulk without a brane?
  We suggest a braneless scenario that still hides large-volume extra dimensions. Ordinarily the strength of bulk gauge interactions would be diluted over the large internal volume, making all the four dimensional forces weak. We use the fact that if the gauge fields result from the dimensional reduction of pure higher-dimensional gravity, then the strengths of the four dimensional gauge interactions are related to the sizes of corresponding cycles averaged over the compact internal manifold. Therefore, if a gauge force is concentrated over a small cycle it will not be diluted over the entire manifold. Gravity, however, remains diluted over the large volume. Thus large-volume, large mass gap extra dimensions with small cycles can remain hidden and result in a hierarchy between gravity and the other forces. However, problematically, the cycles are required to be smaller than the higher-dimensional Planck length and this raises concern over quantum gravity corrections. We speculate on possible cures. 
Kurt Hinterbichler, Janna Levin, Claire Zukowski
hep-th gr-qc hep-ph