Selfconsistent calculations of spectral densities in the O(N) model: Improving the Hartree-Fock approximation by including nonzero decay widths
Mar, 2005Citations per year
Abstract: (Elsevier)
We study the linear sigma model with O ( N ) symmetry at nonzero temperature in the framework of the Cornwall–Jackiw–Tomboulis formalism. Extending the set of two-particle irreducible diagrams by adding sunset diagrams to the usual Hartree–Fock contributions, we derive a new approximation scheme which extends the standard Hartree–Fock approximation by the inclusion of nonzero decay widths. In this approximation, in-medium modifications of the meson masses as well as decay and collisional broadening effects are self-consistently taken into account. As compared to the standard Hartree–Fock approximation, the temperature for the chiral symmetry restoring phase transition is lowered by ∼ 20 – 25 % . For large temperatures, the spectral densities of the σ -meson and the pion become degenerate, as required for the chirally symmetric phase.- 12.40.Yx
- 11.10.Wx
- 12.38.Lg
- sigma model: linear
- symmetry: O(N)
- finite temperature
- Hartree-Fock approximation
- symmetry: chiral
- critical phenomena
- meson: mass
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