Showing papers on "Nuclear matter published in 1989"
TL;DR: The purpose of this chapter is to review this “traditional” approach in the area of nuclear forces and their applications to nuclear structure.
Abstract: Nowadays it has become customary in nuclear physics to denote by “tradition” the approach that considers nucleons and mesons as the relevant degrees of freedom. It is the purpose of this chapter to review this “traditional” approach in the area of nuclear forces and their applications to nuclear structure.
1,049 citations
TL;DR: The relativistic mean field model of the nucleus is reviewed in this article, where the meson fields are treated as mean fields, i.e. as nonquantal c-number fields, and the effect of the Dirac sea of the nucleons is neglected.
Abstract: The relativistic mean-field model of the nucleus is reviewed. It describes the nucleus as a system of Dirac nucleons which interact in a relativistic covariant manner via meson fields. The meson fields are treated as mean fields, i.e. as non-quantal c-number fields. The effect of the Dirac sea of the nucleons is neglected. The model is interpreted as a phenomenological ansatz providing a self-consistent relativistic description of nuclei and nuclear dynamics. It is viewed, so to say, as the relativistic generalisation of the Skyrme-Hartree-Fock ansatz. The capability and the limitations of the model to describe nuclear properties are discussed. Recent applications to spherical and deformed nuclei and to nuclear dynamics are presented.
704 citations
TL;DR: In this paper, a microscopic theory based on orthogonal correlated basis functions is developed for the single-particle spectral function of an infinite Fermi system, where spin-isospin and tensor correlations are fully taken into account.
192 citations
TL;DR: It is shown that a natural extension of the Gell-Mann--Levy model incorporates a parametrization of the dependence of the baryon-doublet masses on the quark mass and predictions of this candidate effective model for the hadronic component of high-density and high-temperature nuclear matter are discussed.
Abstract: Recent lattice-gauge-theory simulations at finite temperatures have suggested that chiral-symmetry restoration at finite temperatures entails parity doubling of the baryon spectrum. We show that a natural extension of the Gell-Mann--L\'evy model incorporates this effect. Predictions of this candidate effective model for the hadronic component of high-density and high-temperature nuclear matter are discussed. The model suggests a parametrization of the dependence of the baryon-doublet masses on the quark mass. This parametrization is compared with the recent lattice results.
181 citations
TL;DR: It is shown that the nucleon-antinucleon pair term required in the analysis of meson-exchange currents has a genuine three-body counterpart resulting from time-ordered diagrams containing a single {ital Z} branch, which achieves the important saturating effect present in relativistic mean-field approaches.
Abstract: Describing an assembly of an infinite number of nucleons in interaction via a two-body potential as a nonrelativistic many-body problem in the first place, we envisage corrections to this picture due to suppressed degrees of freedom at the level of the two-body potential At variance with relativistic many-body theory, the solution of the nonrelativistic problem with a two-body potential only is sufficiently under control at present so that evaluating corrections in this framework is of particular interest These corrections come primarily from additional three-body forces either due to finite-density effects (Pauli blocking of fermions) or are of genuine origin: relativistic dynamical processes and effects from the intrinsic structure of the nucleon Recalling the successful treatment of electromagnetic interactions in nuclei in terms of meson-exchange currents, we establish novel consistency requirements between the initial two-body force and the well-identified residual three-body force In this way no new parameters enter in the three-body force, save for the controversial mass of the fictitious scalar ``\ensuremath{\sigma}'' meson We show further that the nucleon-antinucleon pair term required in the analysis of meson-exchange currents has a genuine three-body counterpart resulting from time-ordered diagrams containing a single Z branch Its contribution to the energy per particle is repulsive and varies with a high power of the density Thereby we obtain the important saturating effect present in relativistic mean-field approaches We envisage next the role of the first radial nucleon resonance ${N}^{\mathrm{*}}$((1/2,1)/2) (Roper resonance) in inducing a specific three-body force The meson-nucleon-Roper coupling constants and form factors are evaluated in a relativistic quark model Gathering all self-consistent corrections to the binding energy per particle of infinitely many nucleons, we find that the final equation of state is solely governed by the density dependence of medium corrections to the free \ensuremath{\sigma}-meson mass We discuss a first attempt to extract this density dependence from an empirical equation of state
155 citations
TL;DR: A striking difference exists in the size of the Fermi surface anomaly in the two cases, and the physical origins of the effective mass are shown to be very different in the relativistic and nonrelativistic descriptions.
Abstract: In relativistic descriptions of the mean field in nuclei or in nuclear matter, the expression ``effective mass'' has been used to denote different quantities. The relationship between these various quantities is clarified. It is exhibited which one among them is most closely related to the effective mass that is derived from nonrelativistic analyses of scattering and bound-state data. This nonrelativistic-type effective mass has a characteristic energy dependence near the Fermi energy whenever one goes beyond the relativistic Hartree or Hartree-Fock approximations. By making use of dispersion relations that connect the real and imaginary parts of the microscopic mean field, it is shown that the occurrence of this ``Fermi surface anomaly'' is quite general. It has the same origin as in the nonrelativistic case, namely the frequency dependence of the mean field. Despite this qualitative similarity between the relativistic and nonrelativistic cases, a striking difference exists between the size of the Fermi surface anomaly in the two cases. The physical origins of the effective mass are also shown to be very different in the relativistic and nonrelativistic descriptions.
143 citations
TL;DR: The bulk viscosity of neutron-star matter, arising from the time lag in achieving beta equilibrium as the density is changed, is calculated and it is found that at temperatures above 10/sup 9/ K the bulk viscoity may dominate the dissipation term which regulates the gravitational-wave instability of rapidly rotating neutron stars.
Abstract: The bulk viscosity of neutron-star matter, arising from the time lag in achieving beta equilibrium as the density is changed, is calculated. In the model used in standard cooling calculations, it is found, for the case of normal neutron matter, that the bulk viscosity goes as the sixth power of the temperature (as compared with a ${T}^{\mathrm{\ensuremath{-}}2}$ dependence for the shear viscosity), and that at temperatures above ${10}^{9}$ K the bulk viscosity may dominate the dissipation term which regulates the gravitational-wave instability of rapidly rotating neutron stars. This raises the possibility that in the first years of a neutron-star's life the star could become unstable as the bulk viscosity decreases through cooling, with potentially observable consequences.
133 citations
TL;DR: In this paper, the authors present a simple equation of state that yields, in the non-rotating case, maximally compact models of neutron stars, and argue that stars constructed in this way will also be stable when rotating with periods < 0.5 ms.
Abstract: IF the submillisecond pulsar in the remnant of supernova 1987A really is rotating stably with a period Psmp of 0.508 ms (ref. 1), its existence can be used to rule out nearly all 'realistic' equations of state for dense nuclear matter. (An alternative hypothesis, that the pulsar is vibrating rather than rotating2, yields no such constraints.) We present here a simple equation of state that yields, in the non-rotating case, maximally compact models of neutron stars, and argue that stars constructed in this way will also be stable when rotating with periods <0.5 ms. Additional constraints found by applying the same equation of state to the 'slowly' rotating pulsar PSR1913 + 16, whose mass is accurately known, leaves only a small range of acceptable parameters for neutron star models based on equations of state that obey the causality requirement that their sound speeds are less than the speed of light.
121 citations
TL;DR: In this article, the self-consistency between the ladders and the self energy is established for the quasi-particle energy, and a careful study of the complete momentum and energy dependence of the resulting self-energy is made for various densities.
109 citations
CERN1
TL;DR: In this article, a new representation of the partition function for strong-coupling QCD is presented, which is suitable also for finite baryon-number density simulations.
100 citations
TL;DR: A review of experimental and theoretical works which support this statement is given in this paper, where the authors show how it has been possible to experimentally establish that very hot equilibrated nuclei are really formed.
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TL;DR: The theory of hot nuclear matter has been developed primarily to help understand some aspects of highly excited nuclei, heavy-ion reactions, supernova and neutron stars as discussed by the authors, and its phase diagram.
Abstract: The theory of hot nuclear matter has been developed primarily to help understand some aspects of highly excited nuclei, heavy-ion reactions, supernova and neutron stars. In the next two sections we review some of the basic concepts of quantum statistical mechanics and nuclear forces. The results of rather simplistic calculations of hot nuclear matter and its phase diagram are given in Section IV. Topics of special interest including instabilities in hot nuclear matter and very hot nuclear matter are briefly discussed in sections V–VIII.
TL;DR: In this paper, the authors studied relativistic nuclear field theory with and without vacuum renormalization for nuclear and neutron star matter in general equilibrium, and neutron stars in particular.
TL;DR: In this paper, the orthogonalized version of correlated basis theory is used to evaluate the longitudinal response of nuclear matter from realistic nuclear interaction, and the correlated 1plh excited states have been fully retained in the calculation.
TL;DR: In this article, a review of high-energy nucleus-nucleus collisions is presented, covering particle spectra, rapidity and multiplicity distributions, composite particle production, and collective flow variables.
Abstract: Recent data on high-energy nucleus-nucleus collisions are reviewed, covering particle spectra, rapidity and multiplicity distributions, composite particle production, and collective flow variables. Emphasis is placed both on the basic physical observables, which guide us in the understanding of the gross features of the reaction mechanism, and on the discovery of strong collective phenomena in particle emission, which generated the grounds for recent progress made in determining the equation of state of hot compressed nuclear matter. A review of appropriate techniques for this purpose is followed by a summary of recent experimental data and by a discussion about their implications on the determination of the nuclear equation of state.
TL;DR: Two-loop corrections for nuclear matter, including vacuum polarization, are calculated in the Walecka model to study the loop expansion as an approximations scheme for quantum hadrodynamics and indicate that the loopexpansion is not convergent at two-loop order in either the strong or weaksense.
Abstract: Two-loop corrections for nuclear matter, including vacuum polarization, are calculated in the Walecka model to study the loop expansion as an approximation scheme for quantum hadrodynamics. Criteria for useful approximation schemes are discussed, and the concepts of strong and weak convergence are introduced. The two-loop corrections are evaluated first with one-loop parameters and mean fields and then by minimizing the total energy density with respect to the scalar field and refitting parameters to empirical nuclear matter saturation properties. The size and nature of the corrections indicate that the loop expansion is not convergent at two-loop order in either the strong or weak sense. Prospects for alternative approximation schemes are discussed.
TL;DR: A model for a relativistic many-body system at finite temperature in the framework of thermo field dynamics, which is a real-time formalism of finite-temperature field theory, which contains the scalar and the vector mesons as well as the Dirac nucleon.
Abstract: We propose a model for a relativistic many-body system at finite temperature in the framework of thermo field dynamics, which is a real-time formalism of finite-temperature field theory. Our model contains the scalar (\ensuremath{\sigma}) and the vector (\ensuremath{\omega}) mesons as well as the Dirac nucleon. The full propagator and self-energy for each particle are presented in terms of spectral representations. The Feynman rules for a perturbation expansion are shown. They are applied to the study of collective modes in hot and dense matter within the random-phase approximation. The dispersion relations of the longitudinal and transverse collective modes in the meson branch are calculated. We also estimate the effective meson mass which is defined as the energy needed to create one meson at rest in extreme matter. The effects of vacuum fluctuations are also examined. They contribute a fair amount to the collective modes through the effective nucleon mass.
TL;DR: In this paper, the bulk viscosity arising from non-leptonic strangeness-changing quark-quark interactions is calculated for ordinary nuclear matter, and the gravitational wave secular instability should be completely suppressed for quark stars and the damping times for pulsations will be very short.
TL;DR: In this paper, a new first-order phase transition at finite baryon density is shown to occur using an effective lagrangian which simulates the parity doubling of the nucleon found recently in lattice QCD.
TL;DR: In this paper, the pairing properties of Gogny's effective interaction for infinite nuclear matter were studied and the solution of the HFB equations yields a relatively high value of Δ nm ⋍ 0.7 MeV for nuclear matter at saturation.
TL;DR: In the framework of relativistic hydrodynamics various shock-wave configurations for a medium with anomalous thermodynamical properties are considered and a broad region of constant specific entropy is found which may serve as a useful signal for the deconfinement transition.
Abstract: In the framework of relativistic hydrodynamics various shock-wave configurations for a medium with anomalous thermodynamical properties are considered. The generalized shock adiabatic is constructed and applied to relativistic nuclear collisions in an energy region where the deconfinement transition is expected. Different forms of the hadron-matter equation of state and their possible experimental consequences for relativistic nuclear collisions are disussed. We find for particular equations of state a broad region of constant specific entropy which may serve as a useful signal for the deconfinement transition.
TL;DR: The lattice Hamiltonian method for solving the Vlasov equation with exact energy conservation is developed, with a view to understanding low-energy phenomena in heavy-ion collisions.
Abstract: The lattice Hamiltonian method for solving the Vlasov equation with exact energy conservation is developed, with a view to understanding low-energy phenomena in heavy-ion collisions. An accurate method of creating initial nuclear ground states is presented, and breathing mode excitations in these states are studied. Heavy-ion collisions are simulated using classical and Thomas-Fermi time-dependent mean field theory to study the effects of the quantum Fermi motion in such collisions.
TL;DR: In this paper, a relativistic model of baryons interacting via the exchange of σ-, ω-, π- and ρ-mesons (SVI) is used to describe the properties of both dense and superdense matter.
TL;DR: In this paper, the stability of strongly ssymmetric nuclear matter with a small proton admixture was investigated and conditions under which strongly symmetric nuclear material could acquire a permanent magnetization.
01 Jan 1989
TL;DR: The Winter School "Nuclear Matter and Heavy Ion Collisions" as mentioned in this paper was devoted to recent developments in nuclear matter theory and to the study of central heavy ion collisions in which quasi macroscopic nuclear systems can be formed at various temperatures and densities.
Abstract: The Winter School "Nuclear Matter and Heavy Ion Collisions," a NATO Research Workshop held at Les Houches in February 89, has been devoted to recent developments in nuclear matter theory and to the study of central heavy ion collisions in which quasi macroscopic nuclear systems can be formed at various temperatures and densities At in cident energies below 100 Me V per nucleon, the kinematic conditions are favourable for producing transient hot nuclei with temperatures of the order of a few MeV At higher ener gies (100 MeV
TL;DR: In this paper, a possible scenario driven by QCD deconfinement in a high density nuclear matter medium is presented, and the expected consequences for type II supernovae explosions are also given, particularly, the output energy that might be enough to account for the observed events.
Abstract: We present a possible scenario driven by QCD deconfinement in a high density nuclear matter medium. Some expected consequences for type II supernovae explosions are also given, particularly, the output energy that might be enough to account for the observed events.
TL;DR: In this article, a variational moment approach was used to predict the properties of low-energy protons from the extrapolation of the optical-model potential, which was adapted to the case of protons in 208 Pb.
TL;DR: In this paper, both the nucleon-nucleon inelastic and the kaon-production cross sections in dense nuclear matter are evaluated in the one-pion exchange model.
TL;DR: In this paper, the σ- and π-meson propagators were calculated in dense baryonic matter and the vacuum was described by a Nambu-Jona-Lasinio model of quarks.
TL;DR: It is shown that at higher temperatures (Tgreater than or equal to20 MeV), strange matter boils, with bubbles of hadronic gas forming and growing throughout the interior.
Abstract: Strange matter is a form of quark matter that has been conjectured to be stable at zero temperature. If heated to a temperature Tgreater than or equal to2 MeV, a strange-matter lump evaporates nucleons from its surface. We show that at higher temperatures (Tgreater than or equal to20 MeV), strange matter boils, with bubbles of hadronic gas forming and growing throughout the interior. Strange matter, or any other phase which resembles strange matter, could not have survived this process in the early Universe.