Würzburg 2018 – scientific programme

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GR: Fachverband Gravitation und Relativitätstheorie

GR 15: Quantum Gravity II

GR 15.2: Talk

Friday, March 23, 2018, 09:15–09:30, NW-Bau - HS3

Semiclassical approximation to quantum geometrodynamics of Weyl-Einstein gravity and emergence of classical Einstein gravity — Claus Kiefer and •Branislav Nikolic — Institute for Theoretical Physics, Zülpicher Straße 77a, 50937 Cologne, Germany

It is known that a semiclassical approximation to the quantum geometrodynamics based on the Einstein-Hilbert action gives, to the highest order, classical Einstein gravity, while the following order gives the quantum field theory on curved spacetimes in the Schrödinger picture, which is a desirable result. In addition, higher derivative classical theories of gravity are being investigated as alternatives to or extensions of General Relativity. If one wants to study quantum gravity via quantum geometrodynamics, it is natural to investigate whether such alternative theories emerge in the semiclassical approximation to their corresponding quantum gravity theories. We study a particular theory of Weyl-Einstein gravity, in which the Einstein-Hilbert action is extended to include the quadratic Weyl tensor term. It is shown that an appropriate semiclassical approximation, motivated by the method of perturbative constraints, does not lead to the classical Weyl-Einstein gravity, but to the classical Einstein equations. Signatures of the Weyl-tensor term appear in the following order, where a modified functional Schrödinger equation emerges. We discuss the implications of these results.