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Quantum mean-field theory of collective dynamics and tunneling

Description: A fundamental problem in quantum many-body theory is formulation of a microscopic theory of collective motion. For self-bound, saturating systems like finite nuclei described in the context of nonrelativistic quantum mechanics with static interactions, the essential problem is how to formulate a systematic quantal theory in which the relevant collective variables and their dynamics arise directly and naturally from the Hamiltonian and the system under consideration. Significant progress has been made recently in formulating the quantum many-body problem in terms of an expansion about solutions to time-dependent mean-field equations. The essential ideas, principal results, and illustrative examples are summarized. An exact expression for an observable of interest is written using a functional integral representation for the evolution operator, and tractable time-dependent mean field equations are obtained by application of the stationary-phase approximation (SPA) to the functional integral. Corrections to the lowest-order theory may be systematically enumerated. 6 figures. (RWR)
Date: January 1, 1981
Creator: Negele, J.W.
Partner: UNT Libraries Government Documents Department

Time independent mean-field theory

Description: The physical and theoretical motivations for the time-dependent mean-field theory are presented, and the successes and limitations of the time-dependent Hartree-Fock initial-vaue problem are reviewed. New theoretical developments are described in the treatment of two-body correlations and the formulation of a quantum mean-field theory of large-amplitude collective motion and tunneling decay. Finally, the mean-field theory is used to obtain new insights into the phenomenon of pion condensation in finite nuclei. 18 figures.
Date: February 1, 1980
Creator: Negele, J.W.
Partner: UNT Libraries Government Documents Department

Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD

Description: Moments of the quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD. Calculations of proton matrix elements of operators corresponding to these moments through the operator product expansion have been performed on the 16{sup 3} x 32 lattices for Wilson fermions at Beta=5.6 using configurations from the SESAM collaboration and at Beta = 5.5 using configurations from SCRI. One-loop perturbative renormalization corrections are included. At quark masses accessible in present calculations, there is no statistically significant difference between quenched and full QCD results, indicating that the contributions of quark-antiquark excitations from the Dirac Sea are small. Close agreement between calculations with cooled configurations containing essentially only instantons and the full gluon configurations indicates that quark zero modes associated with instantons play a dominant role. Naive linear extrapolation of the full QCD calculation to the physical pion mass yields results inconsistent with experiment. Extrapolation to the chiral limit including the physics of the pion cloud can resolve this discrepancy and the requirements for a definitive chiral extrapolation are described.
Date: January 1, 2002
Creator: Dolgov, D.; Brower, R.; Capitani, S.; Dreher, P.; Negele, J.W.; Pochinsky, A. et al.
Partner: UNT Libraries Government Documents Department

Moments of Structure Functions in Full QCD

Description: Moments of the quark density distribution, moments of the quark helicity distribution, and the tensor charge are calculated in full QCD. Calculations of matrix elements of operators from the operator product expansion have been performed on 16{sup 3} x 32 lattices for Wilson fermions at {beta} = 5.6 using configurations from the SESAM collaboration and at {beta} = 5.5 using configurations from SCRI. One-loop perturbative renormalization corrections are included. Selected results are compared with corresponding quenched calculations and with calculations using cooled configurations.
Date: August 1, 2000
Creator: Dolgov, D.; Brower, R.; Capitani, S.; Negele, J. W.; Pochinsky, A.; Renner, D. et al.
Partner: UNT Libraries Government Documents Department

Continuum Extrapolation of Moments Nucleon Quark Distributions in Full QCD

Description: Moments of light cone quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD at {beta} = 5.5 and {beta} = 5.3 using Wilson fermions on 16{sup 3} x 32 lattices. These results are combined with earlier calculations at {beta} = 5.6 using SESAM configurations to study the continuum limit.
Date: June 1, 2002
Creator: Dreher, P.; Brower, R.; Capitani, S.; Dolgov, D.; Edwards, R.; Eicker, N. et al.
Partner: UNT Libraries Government Documents Department