Some Astrophysical Implications of Compact Extra Dimensions
  There have been many suggestions that there are extra spatial dimensions "outside" of our normal (3+1)-dimensional space. Generally it is assumed that electromagnetic and hadronic fields are restricted to the normal dimensions, while gravity can extend into the extra dimensions. Thus a hadron or lepton is confined in a potential well, and excited states should exist. I explore the possibility that ordinary hadrons and leptons have excited states ("compactons"), some of which may have electromagnetism and possibly gravity confined to the extra spatial dimensions. Some of these may be long-lived. If sufficiently long-lived, relic compactons may exist as dark matter. Black holes may be the source of new particles with bizarre properties that appear as UHE cosmic rays. 
Michael J. Longo (Department of Physics, University of Michigan)