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Phys. Rev. D 74, 025004 (2006) [13 pages]

Nonequilibrium dynamics in the O(N) model to next-to-next-to-leading order in the 1/N expansion

Gert Aarts
Department of Physics, University of Wales Swansea, Singleton Park, Swansea, SA2 8PP, United Kingdom

Anders Tranberg
Department of Physics & Astronomy, University of Sussex, Falmer, Brighton, BN1 9QH, United Kingdom
and DAMTP, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA, United Kingdom

Received 21 April 2006; published 6 July 2006

Nonequilibrium dynamics in quantum field theory has been studied extensively using truncations of the 2PI effective action. Both 1/N and loop expansions beyond leading order show remarkable improvement when compared to mean-field approximations. However, in truncations used so far, only the leading-order parts of the self-energy responsible for memory loss, damping and equilibration are included, which makes it difficult to discuss convergence systematically. For that reason we derive the real and causal evolution equations for an O(N) model to next-to-next-to-leading order in the 2PI-1/N expansion. Because of the appearance of internal vertices the resulting equations appear intractable for a full-fledged 3+1 dimensional field theory. Instead, we solve the closely related three-loop approximation in the auxiliary-field formalism numerically in 0+1 dimensions (quantum mechanics) and compare to previous approximations and the exact numerical solution of the Schrödinger equation.

©2006 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevD.74.025004
DOI: 10.1103/PhysRevD.74.025004
PACS: 11.15.Pg; 05.70.Ln
  • 11.15.Pg
    Expansions for large numbers of components (e.g., 1/Ncexpansions) in gauge theories
  • 05.70.Ln
    Nonequilibrium and irreversible thermodynamics
  • YEAR: 2006

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