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[en] Recent studies have shown that concepts of effective field theory such as naturalness can be profitably applied to relativistic mean-field models of nuclei. Here the analysis by Friar, Madland, and Lynn of naturalness in a relativistic point-coupling model is extended. Fits to experimental nuclear data support naive dimensional analysis as a useful principle and imply a mean-field expansion analogous to that found for mean-field meson models. (orig.)

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31 refs.

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[en] Nuclear matter and ground state properties for (proton and neutron) semi-closed shell nuclei are described in relativistic mean field theory with coupling constants which depend on the vector density. The parametrization of the density dependence for σ-, ω- and ρ-meson coupling is obtained by fitting to properties of nuclear matter and some finite nuclei. The results are compared to density-dependent coupling constants derived from self-energies of Dirac-Brueckner calculations of nuclear matter. The equation of state for symmetric and asymmetric nuclear matter is discussed. Finite nuclei are described in Hartree approximation, including a charge and a centre-of-mass correction. Pairing is considered in the BCS approximation. Special attention is directed to the predictions for properties at the neutron and proton driplines

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S0375947499003103; Country of input: International Atomic Energy Agency (IAEA); Copyright (c) 1999 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.

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[en] The perturbative calculation of the lifetime of charged excitations in ultrarelativistic plasmas is plagued with infrared divergences which are not eliminated by the screening corrections. The physical processes responsible for these divergences are the collisions involving the exchange of long-wavelength, quasistatic, magnetic gluons (or photons), which are not screened by plasma effects. In QED, the leading divergences can be resummed in a non-perturbative treatment based on a generalization of the Bloch-Nordsieck model at finite temperature. The resulting expression of the fermion propagator is free of infrared problems, and exhibits a non-exponential damping at large times: S

_{R}(t)∼exp{-αTt lnω_{p}t}, where ω_{p}=eT/3 is the plasma frequency and α=e^{2}/4π. (orig.)Primary Subject

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12. international conference on ultra-relativistic nucleus-nucleus collisions (QuarkMatter-12); Heidelberg (Germany); 20-24 May 1996

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[en] The formalism for relativistic continuum Hartree-Bogolyubov (RCHB) theory, which is the extension of the relativistic mean field (RMF) and the Bogolyubov transformation in the coordinate representation, and its application to nickel isotopes are presented. As the RCHB formalism allowsfor the proper description of the coupling between the bound state and the continuum by the pairing force, therefore it is suitable not only for stable nuclei but also the nuclei near the drip line. The pairing correlations are taken into account by both a density-dependent force of zero range and the finite range Gogny force. The development of the formalism and the numerical techniques involved are discussed in detail. The physics from the RCHB and its understanding in the canonical basis are discussed. The RCHB theory is used to describe the chain of nickel isotopes extending from the proton drip line to the neutron drip line. The comparisons of the two neutron separation energies S

_{2n}as well as the neutron, proton and matter rms radii yield excellent agreement between the calculations with both interactions and the experimental values wherever they exist. Predictions have also been made for the drip-line nucleus^{100}Ni. The pairing energies and single particle levels in the canonical bases and their corresponding occupation probabilities turn out to be similar. (orig.)Primary Subject

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26 refs.

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Numerical Data

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BOGOLYUBOV TRANSFORMATION, BOUND STATE, CORRELATIONS, GIANT RESONANCE, HARTREE-FOCK-BOGOLYUBOV THEORY, MEAN-FIELD THEORY, NEUTRON DENSITY, NEUTRON SEPARATION ENERGY, NICKEL ISOTOPES, NUCLEAR RADII, NUCLEAR STRUCTURE, NUCLEON-NUCLEON POTENTIAL, PAIRING ENERGY, PAIRING INTERACTIONS, PROTON DENSITY, RELATIVISTIC RANGE, THEORETICAL DATA

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[en] The damping width Γ

^{↓}_{GDR}of the giant dipole resonance, due to its coupling to doorway states, is studied within the framework of the thermal Green's functions theory. It is found that Γ^{↓}_{GDR}reflects the temperature dependence of the single-particle damping width but, as a consequence of the cancellation effects between self-energy and vertex contributions, the coefficient of such a dependence is so small that it can essentially be neglected, within the temperature range of physical interest. (orig.)Primary Subject

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14 refs.

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[en] It is shown that in N≅Z nuclei the effects of isovector pairing and the symmetry energy are intimately related. In particular, in the odd-odd N=Z nuclei these two effect are essentially equal in magnitude, causing near degeneracy of the lowest T=1 and T=0 states and appearance of the T=1 ground state isospin in many such nuclei. Following the earlier work of Jaenecke, it is shown that the global symmetry energy fit can be reproduced using just the excitation energies of the lowest T=3/2 states in N=Z+1 nuclei. Similarly, the global pairing gap fit can be related to the excitation energy of the T=|N-Z|/2+1 states in N≅Z even-A nuclei

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S0375947499004236; Country of input: International Atomic Energy Agency (IAEA); Copyright (c) 2000 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.

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[en] A variety of nuclear reactions at energies close to the Coulomb barrier are used to populate residual nuclei in order to study their structure through methods such as γ-ray spectroscopy. The most common of these is the fusion-evaporation reaction. Recent detailed studies of heavy-ion fusion have shown how this reaction proceeds not through a single Coulomb barrier but through a distribution of barriers whose properties are intimately related to the collective modes of the target and projectile. This paper will explore possible ways of exploiting structure effects in the entrance channel to populate systems of interest in the compound nucleus and its evaporation residues. This leads to a complementarity of charged-particle and γ-ray work. Some comments will also be made on the complementarity of experiments with stable and exotic beams in the same energy region. (orig.)

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6. international conference on nucleus-nucleus collisions (NN-6); Gatlinburg, TN (United States); 2-6 Jun 1997; 15 refs.

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[en] The recently available

^{19}C+^{12}C interaction cross section data at E_{lab}=960A MeV and the longitudinal momentum distribution data at E_{lab}=910A MeV and 88A MeV have been analyzed in a Glauber model approach to investigate the possible ground state configuration of the^{19}C nucleus. A comparative analysis of both these experimental data fails to yield a consistent conclusion regarding possible ground state configuration within the 1σ experimental error bar. It is suggested that a considerable change of the core of^{19}C from the bare^{18}C nucleus may take placeOriginal Title

25.60.Gc; 21.10.Gv; 25.70.De; 27.20.+n; 25.70.Mn; 25.60.Dz; One neutron halo; Interaction cross section; Longitudinal momentum distribution; Glauber model

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S0375947400003067; Copyright (c) 2000 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)

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[en] We review, from an experimental point of view, the current status of ultra-relativistic nuclear collisions with heavy beams. (orig.)

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Conference: Quark-matter 1997; Tsukuba, Ibaraki (Japan); 1-5 Dec 1997; 32 refs.

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Conference; Progress Report

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[en] Self-consistent RPA (SCRPA) theory is developed in the particle-particle (pp) channel. It is pointed out that in this way vertex and self-energy corrections are taken into account on an equal footing whereas in Brueckner-Hartree-Fock (BHF) this is not the case. We discuss in detail the interconnection between both theories and apply them to a model case. Excellent agreement with the exact solution is found for SCRPA where as BHF gives somewhat poorer results. In an appendix it is demonstrated how SCRPA connects to a variational principle and how, for the particle-hole case, sum rules and conservation laws are fulfilled. (orig.)

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29 refs.

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BINDING ENERGY, BRUECKNER METHOD, CONSERVATION LAWS, CORRECTIONS, CORRELATION FUNCTIONS, DYSON REPRESENTATION, GREEN FUNCTION, GROUND STATES, HARTREE-FOCK METHOD, NUCLEAR STRUCTURE, NUCLEAR TEMPERATURE, PARTICLE-HOLE MODEL, RANDOM PHASE APPROXIMATION, SELF-CONSISTENT FIELD, SELF-ENERGY, SUM RULES, TEMPERATURE DEPENDENCE, VARIATIONAL METHODS

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