Are Bulk Axions in Models with Extra, Large, Compact Dimensions   Observable?
  The high degeneracy of KK modes in models which have bulk axions moving in some extra, compact dimensions which are larger than O (Angstrom)strongly tightens the supernova upper bounds on the axion photon coupling making axions practically unobservable. Conversely, discovering axions directly or indirectly will exclude such models. These drastic conclusions are avoided if the supernova and bounds from solar axion searches are relaxed. 
Shmuel Nussinov