Showing papers on "Nuclear matter published in 1987"
TL;DR: In this paper, the relativistic Dirac-Brueckner approach was used to study the properties of both dense and hot symmetric nuclear matter, and the saturation point was found to lie on a Coester line which goes through the empirical value for nuclear matter.
297 citations
TL;DR: In this article, momentum-dependent nuclear interactions (MDI) have a large effect on the dynamics and on the observables of high-energy heavy-ion collisions: a soft potential with MDI suppresses pion and kaon yields much more strongly than a local hard potential and results in transverse momenta intermediate between soft and hard local potentials.
Abstract: We demonstrate that momentum-dependent nuclear interactions (MDI) have a large effect on the dynamics and on the observables of high-energy heavy-ion collisions: A soft potential with MDI suppresses pion and kaon yields much more strongly than a local hard potential and results in transverse momenta intermediate between soft and hard local potentials. The collective-flow angles and the deuteron-to-proton ratios are rather insensitive to the MDI. Only simultaneous measurements of these observables can give clues on the nuclear equation of state at densities of interest for supernova collapse and neutron-star stability.
293 citations
TL;DR: In this article, the relativistic Brueckner-Hartree-Fock approach for dense neutron matter is extended to dense dense matter and contributions arising from tensor interactions due to the exchange of π-and ϱ-mesons and the dependence upon neutron-proton asymmetry.
247 citations
TL;DR: The structure of infinite nuclear matter and finite nuclei is studied in the framework of the relativistic Hartree-Fock approximation to obtain a satisfactory description of binding energies and densities for light as well as heavy nuclei.
Abstract: The structure of infinite nuclear matter and finite nuclei is studied in the framework of the relativistic Hartree-Fock approximation. Particular attention is paid to the contribution of isovector mesons (\ensuremath{\pi},\ensuremath{\rho}). A satisfactory description of binding energies and densities can be obtained for light as well as heavy nuclei. The spin-orbit splittings are well reproduced. Connections with nonrelativistic formulations are also discussed.
191 citations
TL;DR: In this paper, a many-body expansion in terms of ph and Δh excitations and the spin-isospin induced interaction is used to evaluate the Δ self-energy in a nuclear medium.
179 citations
TL;DR: In this article, a new covariant formalism is developed for studying two-baryon correlations in infinite nuclear matter, which is based on renormalizable, relativistic quantum field theories of mesons and baryons (quantum hadrodynamics) and involves a selfconsistent summation of the relativistically ladder diagrams using a quasipotential approximation.
166 citations
TL;DR: The regions of baryon number, charge, and hypercharge in which various decays are allowed are illustrated graphically, and flow lines and accumulation lines for decaying strangelets are obtained.
Abstract: We develop a mass formula for finite lumps of strange quark matter near flavor equilibrium Our Fermi-gas model includes surface tension and Coulomb energy but not quantum-chromodynamic radiative corrections Assuming strange matter is stable in bulk, we investigate the radioactive decays of finite strangelets (clumps of strange matter with baryon number Aapprox <10/sup 7/) We derive conditions governing instability for all decay modes The regions of baryon number, charge, and hypercharge in which various decays are allowed are illustrated graphically, and flow lines and accumulation lines for decaying strangelets are obtained Finally, we present typical histories of decaying strangelets
150 citations
TL;DR: It may be possible to infer the pion dispersion relation in hot and dense nuclear matter by measuring the invariant mass distribution of back-to-back electrons and positrons in the center of mass frame in high energy nucleus-nucleus collisions.
Abstract: The general features of electron-positron emission from high temperature nuclear matter are discussed Estimates are made of the production rates arising from incoherent nucleon-nucleon scattering and from two-pion annihilation It may be possible to infer the pion dispersion relation in hot and dense nuclear matter by measuring the invariant mass distribution of back-to-back electrons and positrons in the center of mass frame in high energy nucleus-nucleus collisions
133 citations
TL;DR: In this article, it was shown that a substantial amount of strange quark-antiquark pair condensates in the nucleon required by the πN sigma term implies that kaons could condense in nuclear matter at a density about three times that of normal nuclear matter.
117 citations
TL;DR: In this paper, zero and finite temperature contributions of ground state correlations to the nuclear mean field are studied in nuclear matter at normal density, where the framework is the nonrelativistic hole line expansion with the Paris potential as the bare NN interaction.
98 citations
TL;DR: In this article, the interaction of high energy protons (between 100 MeV and 20 GeV incident energy) with nuclei is studied in the frame of an intranuclear cascade (INC) model.
TL;DR: Negative pion multiplicity was measured over the range of participant nucleon number 80 ~A < 270 for incident energies from 530 to 1350 MeV/n in the La+ La system to require a stiff nuclear matter equation of state.
Abstract: Negative pion multiplicity was measured over the range of participant nucleon number 80 ~A < 270 for incident energies from 530 to 1350 MeV/n in the La+ La system. Th~ is proportional to A and increases linearly with the c.m. energy. Thermal and potential energies, and temperatures of the maximum density phase of the collision are extracted from the data. The results require a stiff nuclear matter equation of state.
TL;DR: This work calculates the nucleon self-energy and the density-dependent effective NN and N..delta.. cross sections in a nuclear medium and shows a sizable reduction of the pion production cross section and important changes in theelta.. absorption cross sections.
Abstract: Within the relativistic Dirac-Brueckner approach we discuss the properties of highly-energetic nucleons and deltas in dense nuclear matter. The effective NN and N..delta.. interactions are constructed in a fully self-consistent way and reproduce all known properties of nuclear matter. We calculate the nucleon self-energy and the density-dependent effective NN and N..delta.. cross sections in a nuclear medium. Results show a sizable reduction of the ..delta.. (pion) production cross section and important changes in the ..delta.. absorption cross sections.
TL;DR: A comprehensive correlated basis theory for calculating the response functions of nuclear matter from realistic nuclear interactions is presented in this paper, where the effect of 2p-2h excitations are approximately included via real and imaginary parts of the optical potential.
TL;DR: Ground-state properties of even-even nuclei in the s-d shell are calculated using relativistic mean- field models of baryon-meson dynamics that include scalar meson self couplings and the implications for quantum hadrodynamics in the mean-field (Hartree) and one-loop approximations are discussed.
Abstract: Ground-state properties of even-even nuclei in the s-d shell are calculated using relativistic mean-field models of baryon-meson dynamics that include scalar meson self couplings. Axial symmetry is assumed. The systematics of intrinsic quadrupole moments are studied for a variety of parameter sets that are fitted to the same nuclear matter saturation properties. The size of the moment is strongly correlated with the nucleon effective mass M/sup */ and the spin-orbit strength, but is only weakly affected by the compressibility or the surface energy. If parameter sets with accurate spin-orbit strengths are used, the trends for s-d nuclei reproduce experimental systematics and are quantitatively similar to those obtained in nonrelativistic Skyrme-Hartree-Fock calculations. The implications for quantum hadrodynamics in the mean-field (Hartree) and one-loop approximations are discussed.
TL;DR: In this article, an equation of state for cold nuclear matter for the region of densities ρnm−4ρnm, where ρ nm is empirical nuclear-matter density, is constructed.
TL;DR: Real-time finite temperature Green's function methods with pair cutoff approximations are applied to the calculation of the equation of state of symmetric nuclear matter and significant differences are found between the pressure-density isotherms at finite temperature given by different Skyrme interactions, although they give quite similar ground state nuclear matter properties.
Abstract: Real-time finite temperature Green's function methods with pair cutoff approximations are applied to the calculation of the equation of state of symmetric nuclear matter. The liquid-gas and the superconducting second-order phase transitions of nuclear matter are studied using, respectively, the normal and abnormal pair cutoff approximations. Several versions of the Skyrme effective interactions are employed. Significant differences are found between the pressure-density isotherms at finite temperature given by different Skyrme interactions, although they give quite similar ground state nuclear matter properties. The critical temperatures ${k}_{B}$${T}_{c}^{(1)}$ for the liquid-gas phase transition given by various Skyrme interactions range from \ensuremath{\sim}15 to \ensuremath{\sim}20 MeV. A strong dependence of ${k}_{B}$${T}_{c}^{(1)}$ on the combination 3${t}_{1}$+5${t}_{2}$, ${t}_{1}$ and ${t}_{2}$ being two parameters of the Skyrme interaction, is observed. For nuclear matter at normal density, nonvanishing energy gap is obtained only for the Skyrme interactions SkI and SkVI. The critical temperatures for the superconducting second-order phase transitions for these two cases are, respectively, 0.5 and 0.345 MeV. Dependence of the energy gap on the nuclear matter density is discussed.
TL;DR: These orbitals and the self-consistently determined mean fields provide a framework for a detailed investigation of the compressibility as well as other relativistic effects.
Abstract: Relativistic Hartree orbitals for nonspherical (even-even) nuclei have been calculated self-consistently from a Lagrangian field theory using the mean field approximation. All parameters in this model are determined from the properties of infinite nuclear matter, so there are no parameters which can be adjusted in the calculation of the orbitals. The energy levels, rms radii, and quadrupole moments are in qualitative agreement with earlier nonrelativistic calculations and with experiment; however, the overall deformations (which are fixed by the self-consistency) are somewhat smaller than those obtained experimentally and from nonrelativistic calculations. The difference may be due to the large compressibility characteristic of relativistic mean field calculations. These orbitals and the self-consistently determined mean fields provide a framework for a detailed investigation of the compressibility as well as other relativistic effects.
TL;DR: In this paper, the static longitudinal structure function S L ( k ) of 3 H, 3 He and 4 He nuclei and nuclear matter were calculated using realistic wave functions obtained from Faddeev and variational calculations.
TL;DR: In this paper, the authors derived the relativistic quantum transport and constraint equations for the Vlasov-Uehling-Uhlenbeck approach for baryons coupled to scalar and vector mesons.
Abstract: We derive the relativistic quantum transport- and constraint equations for a relativistic field theory of baryons coupled to scalar and vector mesons. We extract a selfconsistent momentum dependent Vlasov term and the structure of quantum corrections for the Vlasov-Uehling-Uhlenbeck approach. The inclusion of pions and deltas into this transport theory is discussed.
TL;DR: In this article, the density behavior of topological chiral bags in a baryonic environment was studied using a lattice and a Wigner-Seitz approach, and the reliability of both schemes was compared with experimental data.
TL;DR: The results of the Brueckner calculation for nuclear matter at finite temperature are used to evaluate the renormalization factor in a local and thermal approximation of the nucleon-nucleon interaction.
Abstract: With the assumption that the Brueckner g matrix provides the suitable renormalization of the nucleon-nucleon interaction due to medium effects in the collision term of the nuclear Landau-Vlassov equation, we use the results of our Brueckner calculation for nuclear matter at finite temperature to evaluate the renormalization factor in a local and thermal approximation.
TL;DR: In this paper, a chiral field theory for nuclear matter purely based on fermionic degrees of freedom is presented, and the Nambu-Jona-Lasinio symmetry breaking mechanism is applied in order to obtain a nonvanishing density dependent effective mass of the nucleon.
TL;DR: In this article, the authors investigated the energy and chemical potential of quark matter with strangeness per baryon of order unity in the region near nucleon matter densities.
TL;DR: In this paper, the conditions under which density fluctuations may grow during the expansion of a sphere of heated or super-dense nuclear matter are examined theoretically and the growth rates and accumulated growth factors depend sensitively on the wavenumbers of the fluctuations.
TL;DR: In this paper, the density of the hadron-quark phase transition is determined by one free parameters, which is the energy/volume needed to create a bubble that confines the quarks and gluons.
TL;DR: In this article, three-vector currents for nuclear matter with one valence particle outside a filled Fermi sphere are studied in the mean-field approximation to the Walecka model.
TL;DR: In this article, the authors studied the effect of the baryon-antibaryon pairs on the spectrum of black-body radiation in the abnormal phase of a nuclear nuclear field.
TL;DR: In this paper, a previously developed dispersion relation approach is used to calculate the shell-model potential in the case of neutrons in 208Pb, in the energy domain (-50 MeV, 0).
TL;DR: In this paper, the authors calculate photon emission spectra from nuclear matter in the incoherent limit and combine them with a simplified fireball model to predict photon production cross sections in heavy ion collisions.