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Quantum-to-classical transition of primordial cosmological perturbations in de Broglie-Bohm quantum theory: The bouncing scenario
Phys. Rev. D 89, 023517 – Published 14 January, 2014
DOI: https://doi.org/10.1103/PhysRevD.89.023517
Abstract
In a previous work we have exhibited a clear description of the quantum-to-classical transition of cosmological quantum fluctuations in the inflationary scenario using the de Broglie–Bohm quantum theory. These fluctuations are believed to seed the small inhomogeneities, which are then responsible for the formation of large scale structures. In this work we show that using the de Broglie–Bohm theory, it is also possible to describe the quantum-to-classical transition of primordial perturbations which takes place around a bouncing phase, even if the latter is caused by quantum effects due to the quantization of the background geometry.
Article Text
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In fact, as and depend on , this assertion depends on the scale we are talking about. For an almost scale-invariant spectrum of cosmological perturbations, the term is larger than the term for all scales of cosmological interest (see Ref. [28]), which enforces the argumentation described below for the transition of quantum-to-classical behavior in bouncing models. Only for very short wavelengths can the term be bigger than .
We added the subscript in the equation of state parameter of the fluid dominating the bounce to distinguish it from the equation of state parameter of the dust fluid (like dark matter) which dominated the Universe at the beginning of the contracting phase, when the Universe was very large. While (which leads to an almost scale-invariant spectrum—which is observed—for wavelengths that become longer than the curvature scale during the contracting phase [28]), we have that is of the order of one. For example, in the case of radiation or in the case of stiff matter .