Origin of classical structure from inflation

Abstract

According to the inflationary scenario, all structure in the Universe can be traced back to quantum fluctuations of the metric and scalar field(s) during inflation. The seeds of this structure can be observed as classical anisotropies in the cosmic microwave background. I briefly review how the transition from the inherent quantum nature of these fluctuations to classical behaviour comes about. Two features play a crucial role: Firstly, the quantum state of the fluctuations becomes highly squeezed for wavelengths that exceed the Hubble radius. Secondly, decoherence due to other fields distinguishes the field-amplitude basis as the classical pointer basis. I also discuss the entropy of the fluctuations and make a brief comparison with chaotic systems.

4 pages, needs Elsevier macro espcr2.sty, contribution to the Third Meeting on Constrained Dynamics and Quantum Gravity, Sardegna 1999

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• On the Phase-Space Volume of Primordial Cosmological Perturbations
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• Emergence of inflationary perturbations in the CSL model
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• Inhomogeneities from quantum collapse scheme without inflation
• Classicalization of Quantum Fluctuations at the Planck Scale in the R_h=ct Universe
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• Inflationary gravitational waves in collapse scheme models
• A signature of quantum gravity at the source of the seeds of cosmic structure?
• Enlightening the CSL model landscape in inflation
• Emergent universe revisited through the CSL theory
• Emergent universe: tensor perturbations within the CSL framework
• Observational constraints on the second-order primordial power spectrum: Exploring a Continuous Spontaneous Localization inspired inflationary model
• Quantum Cosmology in $f(Q)$ theory
• On the Quantum-to-Classical Transition of Primordial Perturbations
• A window to quantum gravity phenomena in the emergence of the seeds of cosmic structure