Probabilities in quantum cosmological models: A decoherent histories analysis using a complex potential

Journal Article · Tue Dec 15 00:00:00 EST 2009 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.80.124032· OSTI ID:21316532

Halliwell, J J ^[1]

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1. Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

In the quantization of simple cosmological models (minisuperspace models) described by the Wheeler-DeWitt equation, an important step is the construction, from the wave function, of a probability distribution answering various questions of physical interest, such as the probability of the system entering a given region of configuration space at any stage in its entire history. A standard but heuristic procedure is to use the flux of (components of) the wave function in a WKB approximation. This gives sensible semiclassical results but lacks an underlying operator formalism. In this paper, we address the issue of constructing probability distributions linked to the Wheeler-DeWitt equation using the decoherent histories approach to quantum theory. The key step is the construction of class operators characterizing questions of physical interest. Taking advantage of a recent decoherent histories analysis of the arrival time problem in nonrelativistic quantum mechanics, we show that the appropriate class operators in quantum cosmology are readily constructed using a complex potential. The class operator for not entering a region of configuration space is given by the S matrix for scattering off a complex potential localized in that region. We thus derive the class operators for entering one or more regions in configuration space. The class operators commute with the Hamiltonian, have a sensible classical limit, and are closely related to an intersection number operator. The definitions of class operators given here handle the key case in which the underlying classical system has multiple crossings of the boundaries of the regions of interest. We show that oscillatory WKB solutions to the Wheeler-DeWitt equation give approximate decoherence of histories, as do superpositions of WKB solutions, as long as the regions of configuration space are sufficiently large. The corresponding probabilities coincide, in a semiclassical approximation, with standard heuristic procedures. In brief, we exhibit the well-defined operator formalism underlying the usual heuristic interpretational methods in quantum cosmology.

• OSTI ID: 21316532
• Journal Information: Physical Review. D, Particles Fields, Vol. 80, Issue 12; Other Information: DOI: 10.1103/PhysRevD.80.124032; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CONFIGURATION
COSMOLOGICAL MODELS
COSMOLOGY
DISTRIBUTION
EQUATIONS
HAMILTONIANS
HILL-WHEELER THEORY
MATHEMATICAL SOLUTIONS
POTENTIALS
QUANTIZATION
QUANTUM DECOHERENCE
QUANTUM MECHANICS
S MATRIX
SCATTERING
SEMICLASSICAL APPROXIMATION
SIMULATION
SPACE
WAVE FUNCTIONS
WKB APPROXIMATION