Particles, Waves and Vacuum in Five Dimensions: A Status Report
  Since the 5D canonical metric embeds all 4D vacuum solutions of Einstein's equations, I review its application to the cosmological 'constant', quantized particles, deBroglie waves, scalar fields and wave-particle duality. There are several ways to ra-tionalize these things using an extra dimension. A possible explanation of wave-particle duality is that an observed particle manifests two isometries of flat 5D space in different 4D ways, one with waves and one without. 
Paul S. Wesson
gr-qc