Unitarity of quantum-gravitational corrections to primordial fluctuations in the Born-Oppenheimer approach
TLDR
In this paper, the authors revisited the calculation of quantum-gravitational corrections to the power spectra of scalar and tensor perturbations in the Born-Oppenheimer approach to quantum gravity.Abstract:
We revisit the calculation of quantum-gravitational corrections to the power spectra of scalar and tensor perturbations in the Born-Oppenheimer approach to quantum gravity. We focus on the issue of the definition of the inner product of the theory and the unitarity of the corrections to the dynamics of the cosmological perturbations. We argue that the correction terms are unitary, provided the inner product is defined in a suitable way, which can be related to a notion of gauge fixing the time variable and the use of conditional probabilities in quantum cosmology. We compare the corrections obtained within this framework to earlier results in the literature and we conclude with some remarks on the physical interpretation of the correction terms.read more
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Backreaction in Cosmology
Susanne Schander,Thomas Thiemann +1 more
TL;DR: In this paper, the authors investigate the question of backreaction in different approaches to cosmological perturbation theory, and with a special focus on quantum theoretical aspects, by referring here to the effects of matter field or cosmology inhomogeneities on the homogeneous dynamical background degrees of freedom of cosmology.
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Time in Quantum Cosmology
TL;DR: In this paper , the authors briefly review the problem and illustrate it with two proposed solutions, using the formalism of quantum geometrodynamics, and illustrate the problem with two solutions.
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WKB Approaches to Restore Time in Quantum Cosmology: Predictions and Shortcomings
TL;DR: In this article , the Bianchi IX model is extended to the case of quantum corrections to quantum field theory, where the quantum subsystem is assumed to be made of a quantum variable with two anisotropy degrees of freedom.
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Power spectrum for perturbations in an inflationary model for a closed universe
TL;DR: In this paper , the power spectrum of primordial quantum fluctuations in an inflationary universe for curvature parameter K = 1 was derived through a Born-Oppenheimer type of approximation scheme from the Wheeler-DeWitt equation of canonical quantum gravity using gauge-invariant variables.
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Beyond semiclassical time
TL;DR: In this paper , it was shown that the Born-Oppenheimer approach to the problem of time is an instance of a relational quantum theory, in which transition amplitudes can be related to conditional probabilities.
References
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Zur Quantentheorie der Molekeln
Max Born,Werner Heisenberg +1 more
TL;DR: In der Anwendung der Quantentheorie auf die Molekeln kann man folgende Entwicklungsstufen unterscheiden: Das erste Stadium1) ersetzt die zweiatomige Molekel durch das Hantelmodell, das als einfacher „Rotator“ behandelt wird as discussed by the authors.
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Quantum Theory of Gravity. I. The Canonical Theory
TL;DR: In this article, a 6-dimensional hyperbolic Riemannian manifold is introduced, which takes for its metric the coefficient of the momenta in the Hamiltonian constraint and the geodesic incompletability of this manifold, owing to the existence of a frontier of infinite curvature, is demonstrated.
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Dynamics of phase transition in the new inflationary universe scenario and generation of perturbations
TL;DR: In this article, the dynamics of non-equilibrium phase transition in the early universe are investigated and the transition is triggered by vacuum fluctuations of a Higgs scalar field which determine the duration of an intermediate inflationary stage and the amplitude of adiabatic perturbations.
Quantum Theory of Gravity. I. The Canonical Theory
TL;DR: In this article, a 6-dimensional hyperbolic Riemannian manifold is introduced, which takes for its metric the coefficient of the momenta in the Hamiltonian constraint and the geodesic incompletability of this manifold, owing to the existence of a frontier of infinite curvature, is demonstrated.