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Phys. Rev. D 73, 125002 (2006) [13 pages]

Comparison of Boltzmann equations with quantum dynamics for scalar fields

Manfred Lindner1 and Markus Michael Müller1,2
1Physik-Department T30d, Technische Universität München, James-Franck-Straße, 85748 Garching, Germany
2Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München, Germany

Received 13 January 2006; published 5 June 2006

Boltzmann equations are often used to study the thermal evolution of particle reaction networks. Prominent examples are the computation of the baryon asymmetry of the universe and the evolution of the quark-gluon plasma after relativistic heavy ion collisions. However, Boltzmann equations are only a classical approximation of the quantum thermalization process which is described by the so-called Kadanoff-Baym equations. This raises the question how reliable Boltzmann equations are as approximations to the full Kadanoff-Baym equations. Therefore, we present in this paper a detailed comparison between the Kadanoff-Baym and Boltzmann equations in the framework of a scalar Phi4 quantum field theory in 3+1 space-time dimensions. The obtained numerical solutions reveal significant discrepancies in the results predicted by both types of equations. Apart from quantitative discrepancies, on a qualitative level the universality respected by the Kadanoff-Baym equations is severely restricted in the case of Boltzmann equations. Furthermore, the Kadanoff-Baym equations strongly separate the time scales between kinetic and chemical equilibration. This separation of time scales is absent for the Boltzmann equation.

©2006 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevD.73.125002
DOI: 10.1103/PhysRevD.73.125002
PACS: 11.10.Wx; 12.38.Mh; 98.80.Cq
  • 11.10.Wx
    Finite-temperature field theory
  • 12.38.Mh
    Quark–gluon plasma
  • 98.80.Cq
    Particle-theory and field-theory models of the early Universe (including cosmic pancakes, cosmic strings, chaotic phenomena, inflationary universe, etc.)
  • YEAR: 2006
KEYWORDS: Boltzmann equation, quark-gluon plasma, heavy ion-nucleus reactions, phi4 field theory

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