2003/12/02 by J. Baacke, Baacke, J., Stefan Michalski +1
Chemistry · Physics and Astronomy · #Advanced NMR Techniques and Applications #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th) #Quantum Chromodynamics and Particle Interactions #Theoretical and Computational Physics #hep-ph #hep-th
paper · pdf · doi:10.48550/arxiv.hep-ph/0312031
6 pages. To appear in the proceedings of International Workshop on Quantum Field Theory Under the Influence of External Conditions (QFEXT '03). Norman OK (USA), September 2003
arxiv created 2003/12/02 · openalex publication_date 2003/12/02 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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.