O(N) linear sigma model beyond the Hartree approximation at finite temperature

J. Baacke; Stefan Michalski

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arXiv · hep-ph/0312031

O(N) linear sigma model beyond the Hartree approximation at finite temperature

J. Baacke·Stefan Michalski

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Abstract

We study the O(N) linear sigma model with spontaneous symmetry breaking at finite temperature in the framework of the two-particle point-irreducible (2PPI) effective action. We go beyond the Hartree approximation by including the two-loop contribution, i.e., the sunset diagram. A phase transition of second order is found, whereas it is of first order in the one-loop Hartree approximation. Furthermore, we show the temperature-dependence of the variational mass parameters and comment on their relation to the physical sigma and pion masses.

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J. Baacke, Stefan Michalski. 2003-12-02. O(N) linear sigma model beyond the Hartree approximation at finite temperature. https://arxiv.org/abs/hep-ph/0312031

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