161 citations · 1.3k across the 32 of their papers we have counts for
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gr-qc2021
Power spectrum for perturbations in an inflationary model for a closed universe
Claus Kiefer, Tatevik Vardanyan
We derive the power spectrum of primordial quantum fluctuations in an inflationary universe for curvature parameter . This is achieved through a Born--Oppenheimer t…
gr-qc2021
On a Quantum Weyl Curvature Hypothesis
Claus Kiefer
Roger Penrose's Weyl curvature hypothesis states that the Weyl curvature is small at past singularities, but not at future singularities. We review the motivations for this conject…
gr-qc2021
The impact of Friedmann's work on cosmology
Claus Kiefer, Hermann Nicolai
We present a brief review of Friedmann's impact on cosmology from a historical and a physical perspective.