Higher-Dimensional Communication and S.E.T.I
  In cosmologies with more than four dimensions, of the type required for unification, it is possible for signals to have velocities in excess of that of light. Using a five-dimensional model which otherwise agrees with observations, two subjects are reviewed: (a) An exact solution of the field equations which describes a 4D spacetime with a large cosmological constant and waves travelling in ordinary 3D space with velocities exceeding lightspeed. (b) An example where the 4D interval or proper time is modulated by the systematic variation of the scalar field associated with the fifth dimension, providing a simple signalling method. These and related consequences of higher-dimensional cosmology have significant implications for astrophysics, and especially the Search for Extraterrestrial Intelligence. 
Paul S. Wesson
physics.gen-ph