München 2019 – scientific programme

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GR: Fachverband Gravitation und Relativitätstheorie

GR 8: Quantum Cosmology and Quantum Gravity I

GR 8.3: Talk

Wednesday, March 20, 2019, 15:00–15:15, HS 4

Gauge Fixing and the Semiclassical Interpretation of Quantum Cosmology — •Leonardo Chataignier — Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Cologne, Germany

We make a critical review of the semiclassical interpretation of quantum cosmology and emphasise that it is not necessary to consider that time emerges only when the gravitational field is (semi)classical. We show that the usual results of the semiclassical interpretation can be obtained by a gauge fixing, both at the classical and quantum levels. By ‘gauge fixing’ we mean a particular choice of the time coordinate. In the quantum theory, we adopt a tentative definition of the (Klein-Gordon) inner product, which is positive definite for solutions of the quantum constraint equation found via an iterative procedure that corresponds to a weak coupling expansion in powers of the inverse Planck mass. We conclude that the wave function should be interpreted as a state vector for both gravitational and matter degrees of freedom, the dynamics of which is unitary with respect to the chosen inner product and time variable.