Browsing by Author "Dean Lee, Committee Member"
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- Application of Perturbative and Lattice Techniques to the Analysis of Nuclear Matter.(2010-08-09) Thomson, Richard; Chueng Ji, Committee Chair; Albert Young, Committee Member; Dean Lee, Committee Member; Thomas Schaefer, Committee Member; Sarah Ash, Committee Member
- Applications of canonical transformations and nontrivial vacuum solutions to flavor mixing and critical phenomena in quantum field theory(2004-11-30) Mishchenko, Yuriy; David Brown, Committee Member; Ronald Fulp, Committee Member; Dean Lee, Committee Member; Chueng-Ryong Ji, Committee ChairThis dissertation deals with recent applications of Bogoliubov transformation to the phenomenology of quantum flavor mixing and to the study of critical phenomena in quantum field theories. The dissertation contains a brief review of canonical transformations, with a special emphasis on linear quantum canonical transformation (Bogoliubov transformation), as they appear in classical and quantum physics and their applications in superfluidity and low energy quantum chromodynamics (QCD). Then, the general quantum field theory of flavor mixing is introduced with Bogoliubov transformation, space-time conversion is considered and effects for phenomenology of flavor oscillations in time and space is presented. Furthermore, the Oscillator Representation Method, relevant to analysis of degrees-of-freedom rearrangement during phase transitions, is fully reviewed and illustrated. Nontrivial vacuum condensation, dynamical mass generation and duality are all incorporated as parts of this approach. Specific applications to phase transition in nonlinear sigma model and phi∧4 scalar quantum field theory are presented and possibilities for further method improvement are considered. A new independent variational approach, method of Symmetric Decomposition Problem, is also fully introduced, illustrated and applied to the analysis of the ground state in a variant of nonlinear sigma model. In this method, the structure of the Fock space in terms of the expectation values of given quantum operators is found and used to reformulate and exactly solve variational problem for the ground state of the above mentioned quantum field theory.
- QCD Coulomb Gauge Approach to Exotic Hadrons(2006-12-19) General, Ignacio Jose; Albert Young, Committee Member; Ronald Fulp, Committee Member; Dean Lee, Committee Member; Stephen Cotanch, Committee ChairThe Coulomb Gauge Hamiltonian (CGH) model, a field theoretical, relativistic, many-body approach to Quantum Chromodynamics (QCD),is developed, which describes the vacuum through a Bogoliubov-Valatin transformation. This transformation also dresses the bare quarks and gluons, producing quasi-particles with constituent masses and quark and gluon condensates. This framework is then applied, using the variational principle, to the hybrid meson and tetra-quark problems, where exotic quantum numbers can be generated; light u-ubar-g, strange s-sbar-g and charmed c-cbar-g hybrid meson spectra are calculated and found to agree reasonably well with lattice and Flux Tube predictions. The light tetra-quark spectra is also calculated, along with the charmed tetra-quark structures likely to be the X(3872) and Y(4262) particles. The lowest 1-+ hybrid meson mass is found to be just above 2.2 GeV while the lightest tetra-quark state mass with these exotic quantum numbers is predicted around 1.4 GeV. These theoretical formulations all indicate the observed 1-+ pi 1(1600) and, more clearly, pi 1(1400) are definitely not hybrid states but could be tetra-quark states, with a molecular type, meson-meson structure.
- The Spectrum and Decays of Scalar Mesons in the Light-Front Quark Model(2008-04-25) DeWitt, Martin Alan; Chueng Ji, Committee Chair; Thomas Schaefer, Committee Member; Dean Lee, Committee Member; Orlando Hankins, Committee MemberWe use the light-front quark model to investigate the structure of the scalar mesons, mainly focusing on the three heavy isoscalar states f0(1370), f0(1500), and f0(1710). We comput the spectrum of scalar mesons by diagonalizing a relativized, QCD-inspired model Hamiltonian written in a basis of 25 simple harmonic oscillator states. The masses are then used to perform a mixing analysis which assumes that the heavy isoscalars are mixtures of quarkonia and the scalar glueball. The resulting quark-glue content is used along with the meson wave functions determined from the spectrum to compute the decay rates to pairs of pseudoscalar mesons (two pions, two kaons, two eta mesons). We find that when the glueball contributions to the decays are ignored, the results are in poor agreement with the available data. However, when we estimate the effect of including the glueball contributions in the decays, a solution can be found that matches the data quite well. In this solution, the f0(1710) is mostly glueball (78%) while the f0(1500) and f0(1370) are mostly mixtures of quarkonia. Additionally, in this solution the glueball contributions to kaon and eta final states are significant, while the contributions to the pion final state is negligible. This finding is in agreement with Chanowitz who uses chiral perturbation theory to show that the amplitude for a scalar glueball to decay to a quark-antiquark pair is proportional to the quark mass. This results in a suppression of the pion decay channel compared to the kaon and eta decay channels.
- X-ray Observations of G296.8-00.3.(2010-05-13) Mclaughlin, Letisha; Stephen Reynolds, Committee Chair; Kazimierz Borkowski, Committee Chair; Dean Lee, Committee Member