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Monte Carlo studies of nuclei and quantum liquid drops

Description: The progress in application of variational and Green's function Monte Carlo methods to nuclei is reviewed. The nature of single-particle orbitals in correlated quantum liquid drops is discussed, and it is suggested that the difference between quasi-particle and mean-field orbitals may be of importance in nuclear structure physics. 27 refs., 7 figs., 2 tabs.
Date: January 1, 1989
Creator: Pandharipande, V.R. & Pieper, S.C.
Partner: UNT Libraries Government Documents Department

Nuclear effects in deep inelastic scattering

Description: The authors extend the approach used to treat quasi-elastic inclusive electron-nucleus scattering to the deep inelastic region. They provide a general approach to describe lepton scattering from an off-shell nucleon, and calculate the ratio of inclusive deep inelastic scattering cross sections to the deuteron for nuclear matter and helium (EMC-effect). They find that the consistent inclusion of the binding effects, in particular the ones arising from the short-range nucleon-nucleon interaction, allows to describe the data in the region of x > 0.15 where binding fully accounts for the deviation of the cross section ratios from one.
Date: March 1, 1998
Creator: Benhar, O.; Pandharipande, V.R. & Sick, I.
Partner: UNT Libraries Government Documents Department

Quantum Monte Carlo studies of relativistic effects in light nuclei

Description: Relativistic Hamiltonians are defined as the sum of relativistic one-body kinetic energy, two- and three-body potentials and their boost corrections. In this work the authors use the variational Monte Carlo method to study two kinds of relativistic effects in the binding energy of {sup 3}H and {sup 4}He. The first is due to the nonlocalities in the relativistic kinetic energy and relativistic one-pion exchange potential (OPEP), and the second is from boost interaction. The OPEP contribution is reduced by about 15% by the relativistic nonlocality, which may also have significant effects on pion exchange currents. However, almost all of this reduction is canceled by changes in the kinetic energy and other interaction terms, and the total effect of the nonlocalities on the binding energy is very small. The boost interactions, on the other hand, give repulsive contributions of 0.4 (1.9) MeV in {sup 3}H ({sup 4}He) and account for 37% of the phenomenological part of the three-nucleon interaction needed in the nonrelativistic Hamiltonians.
Date: May 1, 1998
Creator: Forest, J. L.; Pandharipande, V. R. & Arriaga, A.
Partner: UNT Libraries Government Documents Department

Elastic e-d Scattering Data and the Deuteron Wave Function

Description: What range of momentum components in the deuteron wave function are available ed elastic scattering data sensitive to? This question is addressed within the context of a model calculation of the deuteron form factors, based on realistic interactions and currents. It is shown that the data on the A(q), B(q), and T{sub 20}(q) observables at q {le} 6 fm{sup -1} essentially probe momentum components up to {approx} 4m{sub {pi}}.
Date: June 1, 2002
Creator: Schiavilla, R. & Pandharipande, V.R.
Partner: UNT Libraries Government Documents Department

The Charge Form Factors of the Three- and Four-Body Nuclei

Description: The charge form factors of 3H, 3He, and 4He are calculated using the Monte Carlo method and variational ground-state wave functions obtained for the Argonne two-nucleon and Urbana-VII three-nucleon interactions. The model for the charge density operator contains the two-body exchange contributions of longest range. With some spread due to the uncertainty in the electromagnetic form factors of the nucleon the calculated charge form factors are in good agreement with the empirical values over the whole experimentally covered range of momentum transfer.
Date: January 1, 1990
Creator: Schiavilla, R.; Pandharipande, V.R. & Riska, D.O.
Partner: UNT Libraries Government Documents Department

Variational Monte Carlo Calculations of {sup 3}He and {sup 4}He with a Relativistic Hamiltonian - II

Description: In relativistic Hamiltonians the two-nucleon interaction is expressed as a sum of {tilde v}{sub ij}, the interaction in the P{sub ij}=0 rest frame, and the ''boost interaction'' {delta}v(P{sub ij}) which depends upon the total momentum P{sub ij} and vanishes in the rest frame. The {delta}v can be regarded as a sum of four terms: {delta}v{sub RE}, {delta}v{sub LC}, {delta}v{sub TP} and {delta}v{sub QM}; the first three originate from the relativistic energy-momentum relation, Lorentz contraction and Thomas precession, while the last is purely quantum. The contributions of {delta}v{sub RE} and {delta}v{sub LC} have been previously calculated with the variational Monte Carlo method for {sup 3}H and {sup 4}He. In this brief note we report the results of similar calculations for the contributions of {delta}v{sub TP} and {delta}v{sub QM}. These are found to be rather small.
Date: October 1, 1994
Creator: Forest, J.L.; Pandharipande, V.R.; Carlson, J. & Schiavilla, R.
Partner: UNT Libraries Government Documents Department

Variational theory of nuclear and neutron matter

Description: In these lectures we will discuss attempts to solve the A = 3 to {infinity} nuclear many-body problems with the variational method. We choose the form of a variational wave function {Chi}{sub v}(1, 2{hor ellipsis}A) to describe the ground state. The {Chi}{sub v} and the ground-state energy E{sub v} are obtained by minimizing E{sub v} = {l angle}{Chi}{sub v}{vert bar}H{vert bar}{Chi}{sub v}{r angle}/{l angle}{Chi}{sub v}{vert bar}{Chi}{sub v}{r angle} with respect to variations in {Chi}{sub v}. If the form of the variational wave function is chosen properly we can expect {Chi}{sub v} {approx} {Chi}{sub 0} and E{sub v} {approx} E{sub 0} where {Chi}{sub 0} and E{sub 0} are the exact ground-state wave function and energy. In general E{sub v} {ge} E{sub 0} in variational calculations. 63 refs., 11 figs.
Date: June 1, 1989
Creator: Pandharipande, V.R.; Wiringa, R.B. (Illinois Univ., Urbana, IL (USA). Dept. of Physics & Argonne National Lab., IL (USA))
Partner: UNT Libraries Government Documents Department

The nuclear matter problem

Description: We review the present statiis of the many-body theory of nuclear and pure neutron matter based on realistic models of nuclear forces, The current models of two- and three-nucleon interactions are discussed along with recent results obtained with the Brueckner and variatioual methods. New initiatives in the variational method and quantuni Monte Carlo nicthods to study pure neutron matter are described, and finally, the analytic behavior of the energy of piire neutron matter at low densities is cliscussed.
Date: January 1, 2002
Creator: Carlson, J. A. (Joseph A.); Cowell, S.; Morales, J.; Ravenhall, D. G. & Pandharipande, V. R. (Vijay R.)
Partner: UNT Libraries Government Documents Department