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Emergence of classicality for primordial fluctuations: Concepts and analogies

C. Kiefer·D. Polarski
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Abstract

We clarify the way in which cosmological perturbations of quantum origin, produced during inflation, assume classical properties. Two features play an important role in this process: First, the dynamics of fluctuations which are presently on large cosmological scales leads to a very peculiar state (highly squeezed) that is indistinguishable, in a precise sense, from a classical stochastic process. This holds for almost all initial quantum states. Second, the process of decoherence by interaction with the environment distinguishes the field amplitude basis as a robust pointer basis. We discuss in detail the interplay between these features and use simple analogies such as the free quantum particle to illustrate the main conceptual issues.

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C. Kiefer, D. Polarski. 1998-10-16. Emergence of classicality for primordial fluctuations: Concepts and analogies. https://doi.org/10.1002/andp.2090070302

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