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Journal Article

On the Quantum-To-Classical Transition for Ekpyrotic Perturbations

MPS-Authors
http://pubman.mpdl.mpg.de/cone/persons/resource/persons16239

Lehners,  Jean-Luc
String Cosmology, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

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Fulltext (public)

1309.2281.pdf
(Preprint), 9MB

PhysRevD.89_063516.pdf
(Any fulltext), 996KB

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Citation

Battarra, L., & Lehners, J.-L. (2014). On the Quantum-To-Classical Transition for Ekpyrotic Perturbations. Physical Review D, 89: 063516. doi:10.1103/PhysRevD.89.063516.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0014-5424-9
Abstract
We examine the processes of quantum squeezing and decoherence of density perturbations produced during a slowly contracting ekpyrotic phase in which entropic perturbations are converted to curvature perturbations before the bounce to an expanding phase. During the generation phase, the entropic fluctuations evolve into a highly squeezed quantum state, analogous to the evolution of inflationary perturbations. Subsequently, during the conversion phase, quantum coherence is lost very efficiently due to the interactions of entropy and adiabatic modes. Moreover, while decoherence occurs, the adiabatic curvature perturbations inherit their semi-classicality from the entropic perturbations. Our results confirm that, just as for inflation, an ekpyrotic phase can generate nearly scale-invariant curvature perturbations which may be treated as a statistical ensemble of classical density perturbations, in agreement with observations of the cosmic background radiation.