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Classical aspects of quantum fields far from equilibrium.

Gert Aarts1, Jürgen Berges

  • 1Institut für Theoretische Physik, Philosophenweg 16, 69120 Heidelberg, Germany.

Physical Review Letters
|January 22, 2002
PubMed
Summary
This summary is machine-generated.

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The 1/N expansion accurately models quantum scalar field evolution in the O(N) model. Classical physics describes quantum fields at high occupation numbers, but quantum thermal equilibrium eventually causes divergence.

Area of Science:

  • Quantum Field Theory
  • Statistical Mechanics
  • High Energy Physics

Background:

  • Understanding the dynamics of quantum fields out of equilibrium is crucial for various areas of physics.
  • The O(N) model provides a tractable framework for studying many-body quantum systems.

Purpose of the Study:

  • To investigate the time evolution of nonequilibrium quantum scalar fields within the O(N) model.
  • To assess the accuracy of the next-to-leading order 1/N expansion for describing these dynamics.
  • To compare the quantum evolution with classical physics approximations.

Main Methods:

  • Utilizing the two-particle irreducible (2PI) effective action.
  • Employing the next-to-leading order 1/N expansion.
  • Performing exact numerical simulations in 1+1 dimensions for comparison.

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Main Results:

  • The 1/N expansion yields quantitatively precise results for moderate N values.
  • Classical physics accurately describes quantum field evolution for high initial occupation numbers.
  • Deviations arise due to differences between classical and quantum thermal equilibrium.

Conclusions:

  • The 1/N expansion is a reliable tool for studying nonequilibrium quantum field dynamics.
  • Classical approximations are valid under specific conditions but have limitations.
  • The transition to quantum thermal equilibrium marks a breakdown of classical descriptions.