Reflection and transmission at dimensional boundaries
  An inhomogeneous Kaluza-Klein compactification of a higher dimensional spacetime may give rise to an effective 4d spacetime with distinct domains having different sizes of the extra dimensions. The domains are separated by domain walls generated by the extra dimensional scale factor. The scattering of electromagnetic and massive particle waves at such boundaries is examined here for models without warping or branes. We consider the limits corresponding to thin (thick) domain walls, i.e., limits where wavelengths are large (small) in comparison to wall thickness. We also obtain numerical solutions for a wall of arbitrary thickness and extract the reflection and transmission coefficients as functions of frequency. Results are obtained which qualitatively resemble those for electroweak domain walls and other "ordinary" domain walls for 4d theories. 
Nelson De Leon and John Morris