10 papers
Entropy of gravitons produced in the early Universe
C. Kiefer, D. Polarski, A. A. Starobinsky
Gravitons produced from quantum vacuum fluctuations during an inflationary stage in the early Universe have zero entropy as far as they reflect the time evolution (squeezing) of a…
Origin of the inflationary Universe
A. Barvinsky, A. Kamenshchik, C. Kiefer
We give a consistent description of how the inflationary Universe emerges in quantum cosmology. This involves two steps: Firstly, it is shown that a sensible probability peak can b…
Effective action and decoherence by fermions in quantum cosmology
A. Barvinsky, A. Kamenshchik, C. Kiefer
We develop the formalism for the one-loop no-boundary state in a cosmological model with fermions. We use it to calculate the reduced density matrix for an inflaton field by tracin…
Decoherence in quantum cosmology at the onset of inflation
A. Barvinsky, A. Kamenshchik, C. Kiefer +1
We calculate the reduced density matrix for the inflaton field in a model of chaotic inflation by tracing out degrees of freedom corresponding to various bosonic fields. We find a…
Semiclassical Black Hole States and Entropy
T. Brotz, C. Kiefer
We discuss semiclassical states in quantum gravity corresponding to Schwarzschild as well as Reissner Nordström black holes. We show that reduced quantisation of these models is eq…
Ehrenfest's Principle and the Problem of Time in Quantum Gravity
T. Brotz, C. Kiefer
We elaborate on a proposal made by Greensite and others to solve the problem of time in quantum gravity. The proposal states that a viable concept of time and a sensible inner prod…