Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2005-12-12
Phys.Rev.D73:125002,2006
Physics
High Energy Physics
High Energy Physics - Phenomenology
text and figures revised, references added, results unchanged, 21 pages, 10 figures, published in Phys. Rev. D73 (2006) 125002
Scientific paper
10.1103/PhysRevD.73.125002
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 Phi^4 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.
Lindner Manfred
Muller Markus Michael
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