الفهرس 
Color ConfinementOnly 14 pages are availabe for public view
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Abstract
This thesis contains four chapters organized as follows: Introduction, three chapters, the conclusions and future work are presented at the end of chapter four, and a list of references. This thesis is to study the hadron properties at finite temperature and chemical potential in the framework of quantum chromodynamics (QCD) theory, because the equations of this theory are unsolvable, scientists managed to put models and different methods simulate this theory which shares the QCD theory in some properties. The lattice QCD is a method to give an approximate numerical solution to the QCD theory. On the other hand, there are different models that share the QCD theory in some properties, such as, the bag model, the Nambu-Jona-Lasinio model, the Skyrme model, and the linear sigma model. Each of those models has been developed to simulate the QCD theory. The study has shown interest in using extended linear sigma model to study the hadron properties in hot and dense medium, and the chiral phase transition. The thesis comprises of four chapters. Chapter one: We introduce essentials outlines of the following points: The concept of the QCD theory and its properties which are color confinement, asymptotic freedom, and the hidden of chiral symmetry. Next, we present the different methods that are used to solve the QCD theory, such as, the lattice QCD method, and the mean-field quark models. We present the linear sigma model that is used in this study.Chapter two: In this chapter, a logarithmic mesonic potential is proposed for determining nucleon properties. The field equations have been solved in the mean-field approximation. The obtained results of nucleon properties are strongly improved in comparing with the original quark-sigma model. A comparison with the recent quark models is discussed, such as, the extended Skyrme model and the perturbative quark model. Chapter three: The nucleon properties are studied in the extended logarithmic quark sigma model in the hot and dense medium. The logarithmic quark sigma model depends on some aspects of the QCD theory. The field equations have been solved in the mean-field approximation by using extended iteration method at finite temperature and chemical potential . Baryon properties are investigated such as, the hedgehog mass , the magnetic moments of proton and neutron , and the pion-nucleon coupling constant . We find that an increase in both the temperature and baryon chemical potential leads to an increase in the values of the hedgehog mass, proton and neutron magnetic moments, and decrease in the value of the pion-nucleon coupling constant. Chapter four: In the first part of this chapter, the meson masses, the chiral phase transition, the critical temperature are studied in the hot medium using the extended quark sigma model. The quark sigma model is extended to include eighth-order of mesonic interactions based on some aspects of the QCD theory. The extended effective potential tends to the original effective potential when the coupling between the higher-order mesonic interactions equals to zero.