Titel: A computation on whether quantum physics saves determinism
Abstract: There is an ongoing debate whether the Reissner-Nordström-de Sitter spacetime, describing a spherically symmetric charged black hole on a de Sitter background, can be extended beyond the domain of dependence of the initial data, leading to a breakdown of determinism, or whether the slightest generic perturbation of the initial data would lead to the formation of a singularity at the "edge" of that domain, the Cauchy horizon. Recent results have shown that in some regime of the black hole charge and mass, classical scalar perturbations allow for an extension of the spacetime across the Cauchy horizon. In contrast to that, the stress-energy tensor of the quantum scalar field is divergent enough to lead to a singularity at the Cauchy horizon and save determinism, given that the coefficient of its leading divergence is non-zero. To calculate this coefficient, one needs to solve the Klein-Gordon equation for the massive scalar field in this spacetime. This is done semi-analytically. The results show that the coefficient is non-zero for generical spacetime parameters in the regime where classical perturbations allow for a breakdown of determinism.