The cosmological constant as an eigenvalue of a Sturm-Liouville problem and its renormalization

We discuss the case of massive gravitons and their relation with the cosmological constant, considered as an eigenvalue of a Sturm-Liouville problem. A variational approach with Gaussian trial wavefunctionals is used as a method to study such a problem. We approximate the equation to one loop in a Schwarzschild background and a zeta function regularization is involved to handle divergences. The regularization is closely related to the subtraction procedure appearing in the computation of the Casimir energy in a curved background. A renormalization procedure is introduced to remove the infinities together with a renormalization group equation