Problematic aspects of Kaluza-Klein excitations in multidimensional   models with Einstein internal spaces
  We consider Kaluza-Klein (KK) models where internal spaces are compact Einstein spaces. These spaces are stabilized by background matter (e.g., monopole form-fields). We perturb this background by a compact matter source (e.g., the system of gravitating masses) with the zero pressure in the external/our space and an arbitrary pressure in the internal space. We show that the Einstein equations are compatible only if the matter source is smeared over the internal space and perturbed metric components do not depend on coordinates of extra dimensions. The latter means the absence of KK modes corresponding to the metric fluctuations. Maybe, the absence of KK particles in LHC experiments is explained by such mechanism. 
Alexey Chopovsky, Maxim Eingorn and Alexander Zhuk
gr-qc astro-ph.HE hep-ph hep-th