Transport coefficients in quantum chromodynamics

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dc.contributor.advisorCleymans, Jeanen_ZA
dc.contributor.authorVon Oertzen, Detlof Wilhelmen_ZA
dc.date.accessioned2016-10-03T04:10:36Z
dc.date.available2016-10-03T04:10:36Z
dc.date.issued1990en_ZA
dc.description.abstractRelativistic kinetic theory provides a transport equation for classical, spinless, colored particles in a non-Abelian external field. We review the methods of solution used in the literature to find the transport coefficients for quark and gluon systems. Most authors use the relaxation time approximation of the Boltzmann equation to compute the transport coefficients, but this method has shortcomings in mixtures. We use the Chapman Enskog (CE) method to solve the classical transport equations for quarks and gluons for the transport coefficients. The differential crosssections describing the particle interaction are obtained from the lowest order scattering diagrams of quantum chromodynamics. We study a pure quark system, a pure gluon system and a quark antiquark (qq) mixture. For mixtures of quarks, antiquarks and gluons, we find the shear viscosity, heat conductivity and cross-coefficients. The coefficients pertaining to qq mixtures, namely the thermal diffusion, diffusion and Dufour coefficient, the viscosities and heat conductivity are obtained and the conductivity of a qq mixture in an external field is computed. We compare our transport coefficients to others in the literature by rewriting them in terms of characteristic relaxation times. Although our results are generally larger than others, they are of the same order of magnitude, with important implications for quark-gluon (QG) plasma signatures. The quark to gluon shear viscosity ratio is found to be ~5 times the number of quark flavors, emphasising the importance of quarks in dynamical QG calculations. The coefficients for a field-free qq mixture indicate no qq separation in the presence of a temperature gradient. In the CE method, the transport coefficients depend naturally on a logarithmic factor due to the divergent scattering cross-sections, reflecting the plasma shielding effects. This logarithm is evaluated by relating it to typical plasma parameters. We apply our results to the QG phase in the early universe and ultra-relativistic heavy ion collisions. A comparison of the QG to pion transport coefficients at the quark-hadron phase transition shows that the latter are ~10³ smaller. Dissipative effects increase the plasma lifetime, resulting in a longer high energy density and temperature plasma phase.en_ZA
dc.identifier.apacitationVon Oertzen, D. W. (1990). <i>Transport coefficients in quantum chromodynamics</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Physics. Retrieved from http://hdl.handle.net/11427/22057en_ZA
dc.identifier.chicagocitationVon Oertzen, Detlof Wilhelm. <i>"Transport coefficients in quantum chromodynamics."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Physics, 1990. http://hdl.handle.net/11427/22057en_ZA
dc.identifier.citationVon Oertzen, D. 1990. Transport coefficients in quantum chromodynamics. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Von Oertzen, Detlof Wilhelm AB - Relativistic kinetic theory provides a transport equation for classical, spinless, colored particles in a non-Abelian external field. We review the methods of solution used in the literature to find the transport coefficients for quark and gluon systems. Most authors use the relaxation time approximation of the Boltzmann equation to compute the transport coefficients, but this method has shortcomings in mixtures. We use the Chapman Enskog (CE) method to solve the classical transport equations for quarks and gluons for the transport coefficients. The differential crosssections describing the particle interaction are obtained from the lowest order scattering diagrams of quantum chromodynamics. We study a pure quark system, a pure gluon system and a quark antiquark (qq) mixture. For mixtures of quarks, antiquarks and gluons, we find the shear viscosity, heat conductivity and cross-coefficients. The coefficients pertaining to qq mixtures, namely the thermal diffusion, diffusion and Dufour coefficient, the viscosities and heat conductivity are obtained and the conductivity of a qq mixture in an external field is computed. We compare our transport coefficients to others in the literature by rewriting them in terms of characteristic relaxation times. Although our results are generally larger than others, they are of the same order of magnitude, with important implications for quark-gluon (QG) plasma signatures. The quark to gluon shear viscosity ratio is found to be ~5 times the number of quark flavors, emphasising the importance of quarks in dynamical QG calculations. The coefficients for a field-free qq mixture indicate no qq separation in the presence of a temperature gradient. In the CE method, the transport coefficients depend naturally on a logarithmic factor due to the divergent scattering cross-sections, reflecting the plasma shielding effects. This logarithm is evaluated by relating it to typical plasma parameters. We apply our results to the QG phase in the early universe and ultra-relativistic heavy ion collisions. A comparison of the QG to pion transport coefficients at the quark-hadron phase transition shows that the latter are ~10³ smaller. Dissipative effects increase the plasma lifetime, resulting in a longer high energy density and temperature plasma phase. DA - 1990 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1990 T1 - Transport coefficients in quantum chromodynamics TI - Transport coefficients in quantum chromodynamics UR - http://hdl.handle.net/11427/22057 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/22057
dc.identifier.vancouvercitationVon Oertzen DW. Transport coefficients in quantum chromodynamics. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Physics, 1990 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22057en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Physicsen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherPhysicsen_ZA
dc.titleTransport coefficients in quantum chromodynamicsen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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