Selfconsistent approximations, symmetries and choice of representation

Abstract

In thermal field theory selfconsistent (Phi-derivable) approximations are used to improve (resum) propagators at the level of two-particle irreducible diagrams. At the same time vertices are treated at the bare level. Therefore such approximations typically violate the Ward identities connected to internal symmetries. Examples are presented how such violations can be tamed by a proper choice of representation for the fields which describe the system under consideration. These examples cover the issue of massless Goldstone bosons in the linear sigma model and the Nambu--Jona-Lasinio model and the problem of current conservation in theories with massive vector mesons.

13 pages

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Cited by in corpus (12)

• Nonequilibrium chiral fluid dynamics including dissipation and noise
• Electromagnetic transition form factors of light vector mesons
• Chiral QCD sum rules for open charm mesons
• Information on the structure of the a1 from tau decay
• Reactions with pions and vector mesons in the sector of odd intrinsic parity
• The pressure of QED from the two-loop 2PI effective action
• Ward Identities for the 2PI effective action in QED
• Loss of solution in the symmetry improved Phi-derivable expansion scheme
• Soft symmetry improvement of two particle irreducible effective actions
• Short-range correlations in quark matter
• Chiral Partners and their Electromagnetic Radiation -- Ingredients for a systematic in-medium calculation
• Selfconsistent descriptions of vector-mesons in hot matter revisited