Analytical expressions Electrons 6 Energy gap 6 Frequency ranges 6 Metamaterials 6 Negative index 6 Quantum optics 6 Refractive index 6 Three dimensional 6 Above-threshold ionization 4 Bose-Einstein condensation 4 Coherent superpositions 4 Computer simulation 4 Delta functions 4 Diffraction 4 Diffraction process 4 Dinger equation 4 Electric fields 4 Electron gas 4 Electron trajectories 4 Electron-electron interactions 4 Forbidden band 4 GPS 4 Generalized Langevin equation 4 Geometrical relations 4 Global positioning system 4 Gravitational effects 4 Gravity waves 4 High probability 4 Hydrodynamics 4