Casimir Energy of 5D Electro-Magnetism and Sphere Lattice Regularization
  Casimir energy is calculated in the 5D warped system. It is compared with the flat one. The position/ momentum propagator is exploited. A new regularization, called {\it sphere lattice regularization}, is introduced. It is a direct realization of the geometrical interpretation of the renormalization group. The regularized configuration is closed-string like. We do {\it not} take the KK-expansion approach. Instead the P/M propagator is exploited, combined with the heat-kernel method. All expressions are closed-form (not KK-expanded form). Rigorous quantities are only treated (non-perturbative treatment). The properly regularized form of Casimir energy, is expressed in the closed form. We numerically evaluate its $\La$(4D UV-cutoff), $\om$(5D bulk curvature, warpedness parameter) and $T$(extra space IR parameter) dependence. 
Shoichi Ichinose