General Relativity and Quantum Mechanics in Five Dimensions
  In 5D, I take the metric in canonical form and define causality by null-paths. Then spacetime is modulated by a factor equivalent to the wave function, and the 5D geodesic equation gives the 4D Klein-Gordon equation. These results effectively show how general relativity and quantum mechanics may be unified in 5D. 
Paul S. Wesson
physics.gen-ph gr-qc