Decoherence and back reaction in quantum cosmology: Multidimensional minisuperspace examples

Journal Article · Wed Apr 15 04:00:00 EDT 1992 · Physical Review, D (Particles Fields); (United States)

DOI:https://doi.org/10.1103/PhysRevD.45.2823· OSTI ID:7044535

Paz, J P ^[1]; Sinha, S ^[2]

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1. Theoretical Astrophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742 (United States)

We study some aspects of the semiclassical limit of quantum cosmology using multidimensional minisuperspace models with scalar perturbations. Regarding the minisuperspace coordinates as the relevant'' degrees of freedom and the scalar field modes as the irrelevant'' ones, we study the reduced density matrix to analyze the existence of decoherence and correlations. For a Bianchi type-I model we show that the correlations predicted from the peak of the Wigner function associated with a decohered WKB branch are the same as those determined by the semiclassical Einstein equations. We discuss the renormalization of the divergent quantities that appear in the calculation and show that usual dimensional-regularization techniques only allow us to regulate the phase of the reduced density matrix. This illustrates the fundamental difference that exists between the divergences found in the back-reaction equations and the ones that affect the quantum coherence. We analyze a class of models with adiabatic behavior in which there are no problematic divergences affecting the decoherence factor. Finally, we discuss some aspects of the relation between our approach, based on the use of the reduced density matrix, and that formulated in terms of spacetime histories.

• OSTI ID: 7044535
• Journal Information: Physical Review, D (Particles Fields); (United States), Journal Name: Physical Review, D (Particles Fields); (United States) Vol. 45:8; ISSN PRVDA; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

662110* -- General Theory of Particles & Fields-- Theory of Fields & Strings-- (1992-)
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COSMOLOGY
DENSITY MATRIX
FIELD THEORIES
MATRICES
QUANTUM FIELD THEORY
QUANTUM GRAVITY
RENORMALIZATION
SCALAR FIELDS
SPACE-TIME
WKB APPROXIMATION