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Quantum properties of a non-Gaussian state in the large-N approximation
Gautier F., Serreau J.
Physical Review D 83 (2011) 125004 - http://hal.archives-ouvertes.fr/hal-00730838
Physique/Physique des Hautes Energies - Phénoménologie
Physique/Physique des Hautes Energies - Théorie
Physique/Physique Nucléaire Théorique
Physique/Physique Quantique
Quantum properties of a non-Gaussian state in the large-N approximation
F. Gautier, J. Serreau1
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
CNRS : UMR7164 – IN2P3 – Observatoire de Paris – Université Paris VII - Paris Diderot – CEA : DSM/IRFU
APC - UMR 7164, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, case postale 7020, F-75205 Paris Cedex 13
We study the properties of a non-Gaussian density matrix for an O(N) scalar field in the context of the incomplete description picture. This is of relevance for studies of decoherence and entropy production in quantum field theory. In particular, we study how the inclusion of the simplest non-Gaussian correlator in the set of measured observables modifies the effective (Gaussian) description one can infer from the knowledge of the two-point functions only. We compute exactly the matrix elements of the non-Gaussian density matrix at leading order in a 1/N expansion. This allows us to study the quantum properties (purity, entropy, coherence) of the corresponding state for arbitrarily strong non-Gaussianity. We find that if the Gaussian and the non-Gaussian observers essentially agree concerning quantum purity or correlation entropy, their conclusion can significantly differ for other, more detailed aspects such as the degree of quantum coherence of the system.

Physical Review D (Phys. Rev. D)
Publisher American Physical Society
ISSN 1550-7998 (eISSN : 1550-2368)
Articles dans des revues avec comité de lecture

Decoherence – open systems – quantum statistical methods – Theory of quantized fields – Finite-temperature field theory – Particle-theory and field-theory models of the early Universe
14 pages, 7 figures. Published version (Phys. Rev. D, minor corrections)

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