LAUSR

In this work we reexamine the Casimir effect in which the vacuum expectation value of quantum fields is calculated over a so-called Krein space. This method has already been successfully applied to study Casimir effect on non-trivial topologies and also the covariance problem in the massless minimally coupled scalar field in de Sitter space-time. It is shown that within this method, no infinite term appears in the computation of the vacuum expectation value of energy-momentum tensor. We investigate the behavior of the Krein quantization for a scalar field in a box satisfying the Dirichlet boundary condition. We show that one can recover the usual theory with the exception that the vacuum energy of the free theory is zero.