% Encoding: UTF-8
@COMMENT{BibTeX export based on data in FAU CRIS: https://cris.fau.de/}
@COMMENT{For any questions please write to cris-support@fau.de}
@article{faucris.109539144,
abstract = {It is often argued that inflation erases all the information about what took place before it started. Quantum gravity, relevant in the Planck era, seems therefore mostly impossible to probe with cosmological observations. In general, only very ad hoc scenarios or hyper fine-tuned initial conditions can lead to observationally testable theories. Here we consider a well-defined and well-motivated candidate quantum cosmology model that predicts inflation. Using the most recent observational constraints on the cosmic microwave background B-modes, we show that the model is excluded for all its parameter space, without any tuning. Some important consequences are drawn for the deformed algebra approach to loop quantum cosmology. We emphasize that neither loop quantum cosmology in general nor loop quantum gravity are disfavored by this study but their falsifiability is established.},
author = {Bolliet, Boris and Barrau, Aurelien and Grain, Julien and Schander, Susanne},
doi = {10.1103/PhysRevD.93.124011},
faupublication = {no},
journal = {Physical Review D},
peerreviewed = {Yes},
title = {{Observational} exclusion of a consistent loop quantum cosmology scenario},
volume = {93},
year = {2016}
}
@article{faucris.121880924,
abstract = {In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of a Euclidean phase accompanying the nonsingular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power leading to results incompatible with the data.},
author = {Schander, Susanne and Barrau, Aurelien and Bolliet, Boris and Linsefors, Linda and Mielczarek, Jakub and Grain, Julien},
doi = {10.1103/PhysRevD.93.023531},
faupublication = {no},
journal = {Physical Review D},
month = {Jan},
peerreviewed = {Yes},
title = {{Primordial} scalar power spectrum from the {Euclidean} big bounce},
volume = {93},
year = {2016}
}
@article{faucris.277090126,
abstract = {Quantum cosmology, including quantum cosmological inhomogeneities, is a promising framework for describing the very early universe in which all degrees of freedom are being considered as dynamical and quantum. However, many previous discussions on this subject consider the quantum cosmological perturbations as test fields on a curved spacetime with effective quantum modifications and thus neglect certain interactions of the subsystems, namely the backreaction of the inhomogeneous quantum fields on the cosmological background. In a series of four papers, of which this is the first, we aim at improving on the treatment of quantum effects that arise due to backreactions between matter and geometry as well as between the cosmological perturbations and the homogeneous degrees of freedom. We employ the technique of space adiabatic perturbation theory in the form developed by Panati, Spohn, and Teufel which relies on the familiar Born-Oppenheimer approximation. We extend the scheme to quantum field theory in the cosmological perturbative setting and show that this leads to presently neglected correction terms in the quantum Friedmann equations. In this first article, we provide a detailed introduction to the iterative scheme and examine the generic challenges encountered in its application to perturbative quantum cosmology. Our results will allow for a direct comparison to cosmological observations.},
author = {Schander, Susanne and Thiemann, Thomas},
doi = {10.1103/PhysRevD.105.106009},
faupublication = {yes},
journal = {Physical Review D},
note = {CRIS-Team WoS Importer:2022-06-24},
peerreviewed = {Yes},
title = {{Quantum} cosmological backreactions. {I}. {Cosmological} space adiabatic perturbation theory},
volume = {105},
year = {2022}
}
@article{faucris.277091120,
abstract = {In this second paper in a series of four, we continue with the program of incorporating backreaction among the homogeneous and between the homogeneous and inhomogeneous degrees of freedom in quantum cosmological perturbation theory. The purpose of the present paper is to illustrate the formalism of space adiabatic perturbation theory for two simple quantum mechanical models, and to prove that backreaction indeed leads to additional correction terms in effective Hamiltonians that one would otherwise neglect in a crude Born-Oppenheimer approximation. The first model consists of a harmonic oscillator coupled to an anharmonic oscillator. The second model describes the coupling between a scalar matter field and gravity restricted to the purely homogeneous and isotropic sector. These results have potential phenomenological consequences for quantum cosmological models.},
author = {Neuser, Jonas and Schander, Susanne and Thiemann, Thomas},
doi = {10.1103/PhysRevD.105.106010},
faupublication = {yes},
journal = {Physical Review D},
note = {CRIS-Team WoS Importer:2022-06-24},
peerreviewed = {Yes},
title = {{Quantum} cosmological backreactions. {II}. {Purely} homogeneous quantum cosmology},
volume = {105},
year = {2022}
}
@article{faucris.277089876,
abstract = {This is the final paper in a series of four in which we incorporate backreaction among the homogeneous and between the homogeneous and inhomogeneous degrees of freedom in quantum cosmological perturbation theory using space adiabatic methods. Here, we consider the gauge-invariant scalar (Mukhanov-Sasaki) and tensor (primordial gravitational wave) perturbations of general relativity coupled to a scalar field which arise from a careful constraint analysis of this system up to second order in the perturbations. The simultaneous quantization of the homogeneous and inhomogeneous degrees of freedom requires the use of a suitable constructive perturbation scheme for which we employ space adiabatic perturbation theory, a rigorous extension of the standard Born-Oppenheimer theory. We are confronted with several challenges arising for theories with an infinite number of degrees of freedom. We are able to compute the backreaction effects up to second order in the adiabatic parameter and find modifications as compared to earlier derivations of the effective quantum dynamics of the homogeneous sector.},
author = {Schander, Susanne and Thiemann, Thomas},
doi = {10.1103/PhysRevD.105.106012},
faupublication = {yes},
journal = {Physical Review D},
note = {CRIS-Team WoS Importer:2022-06-24},
peerreviewed = {Yes},
title = {{Quantum} cosmological backreactions. {IV}. {Constrained} quantum cosmological perturbation theory},
volume = {105},
year = {2022}
}