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Emergence of classicality for primordial fluctuations: Concepts and analogies
Author(s) -
Kiefer Claus,
Polarski David
Publication year - 1998
Publication title -
annalen der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.009
H-Index - 68
eISSN - 1521-3889
pISSN - 0003-3804
DOI - 10.1002/andp.2090070302
Subject(s) - physics , quantum decoherence , primordial fluctuations , basis (linear algebra) , theoretical physics , inflation (cosmology) , quantum , statistical physics , quantum fluctuation , classical mechanics , quantum mechanics , geometry , mathematics , cosmic microwave background , anisotropy
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 the 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.