Freiburg 2008 – wissenschaftliches Programm

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MP: Fachverband Theoretische und Mathematische Grundlagen der Physik

MP 6: Quantenfeldtheorie

MP 6.4: Vortrag

Mittwoch, 5. März 2008, 18:00–18:20, KGI-HS 1023

Solutions of the semiclassical Einstein equations with possible interpretations in cosmology. — Claudio Dappiaggi, Klaus Fredenhagen, and •Nicola Pinamonti — II. Institut fuer Theoretische Physik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany

In addressing the problem of the definition of a semiclassical Einstein equation, the renormalization of the stress tensor plays a crucial role. We review in detail the case of a scalar field with general mass and general coupling with gravity, where the underlying quantum state is of Hadamard type. Using the ambiguity present in the point splitting procedure, Wald's axioms can be satisfied. We discuss the solutions of the semiclassical Einstein equation with high symmetry: in general they depend upon the quantum state. By means of the proposed method some solution of de Sitter type could arise even if we have not used any cosmological constant. Furthermore these solutions turn out to be stable. Even if the discussed model is very simple it shows that quantum effect are not negligible in addressing similar problems. We discuss some of the implications in cosmology.