On the numerical technique of Casimir energy calculation
  A non-subtractive recipe of Casimir energy renormalization efficient in the presence of logarithmically divergent terms is proposed. It is demonstrated that it can be applied even in such cases, when energy levels can be obtained only numerically whereas neither their asymptotical behavior, nor the analytical form of the corresponding spectral equation can be studied. The results of numerical calculations performed with this method are compared to those obtained by means of explicit subtraction of divergent terms from energy. 
Il.Malakhov, P.Silaev, K.Sveshnikov