On the Effect of Ring Diagrams on QCD Phase Transition

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Salehi Kasmaei, Babak | 2012

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 45432 (04)
University: Sharif University of Technology
Department: Physics
Advisor(s): Sadooghi, Neda
Abstract:
In this thesis NJL and quark-meson models, as eﬀective models for quantum chro-modynamics in low energies, are studied mainly. After reviewing models and phe-nomena related to the strong interaction in zero and non-zero temperature, ﬁrstly the critical coupling of NJL model for non-zero temperature and chemical potential is calculated. Then, the contribution of ring diagrams in the eﬀective potential of quark-meson model is presented. Finaly, the eﬀect of ring diagrams of quark-meson model on chiral phase transition is investigated. For NJL model, it is shown that the chemical potential lowers the critical coupling for chiral phase transition. Also for quark-meson model, it is shown that the contribution of ring diagrams in the eﬀective potential includes odd powers of the coupling and the dynamical quark mass. Finaly, by considering the terms for these diagrams in the total eﬀective potential, its eﬀect on lowering the temperature of phase transition is shown
Keywords:
Ring Diagram ; Effective Model ; Field Theory ; Quantum Chromodynamics (QCD)Phase Transition ; Field Theory in Nonzero Temperature and Chemical Potential Ring Diagrams