Showing papers on "Nuclear matter published in 1994"
TL;DR: In this paper, the authors search for a new parameter set for the description of stable and unstable nuclei in the wide mass range within the relativistic mean-field theory.
719 citations
TL;DR: In this paper, the spectral function P(k, E) of finite nuclei is derived by combining the nuclear-matter correlated part, evaluated in local-density approximation, with the finite-nucleus single-particle part obtained from mean-field calculations or (e, e′p) experiments.
232 citations
TL;DR: In this article, an effective chiral lagrangian in heavy-fermion formalism whose parameters are constrained by kaon-nucleon and kaon nuclear interactions next to the leading order in chiral expansion is used to describe kaon condensation in dense “neutron star” matter.
209 citations
TL;DR: In this article, the authors study the g-mode oscillations of cold neutron stars using microscopic nuclear equations of state, where they determine self-consistently the sound speed and Brunt-Vaisal-a frequency in the nuclear liquid core.
Abstract: Tidal interaction in a coalescing neutron star binary can resonantly excite the g-mode oscillations of the neutron star when the frequency of the tidal driving force equals the intrinsic g-mode frequencies. We study the g-mode oscillations of cold neutron stars using recent microscopic nuclear equations of state, where we determine self-consistently the sound speed and Brunt-V\"ais\"al\"a frequency in the nuclear liquid core. The properties of the g-modes associated with the stable stratification of the core depend sensitively on the pressure-density relation as well as the symmetry energy of the dense nuclear matter. The frequencies of the first ten g-modes lie approximately in the range of $10-100$ Hz. Resonant excitations of these g-modes during the last few minutes of the binary coalescence result in energy transfer and angular momentum transfer from the binary orbit to the neutron star. The angular momentum transfer is possible because a dynamical tidal lag develops even in the absence of fluid viscosity. However, since the coupling between the g-mode and the tidal potential is rather weak, the amount of energy transfer during a resonance and the induced orbital phase error are very small. Resonant excitations of the g-modes play an important role in tidal heating of binary neutron stars. Without the resonances, viscous dissipation is effective only when the stars are close to contact. The resonant oscillations result in dissipation at much larger orbital separation. The actual amount of tidal heating depends on the viscosity of the neutron star. Using the microscopic viscosity, we find that the binary neutron stars are heated to a temperature $\sim 10^8$ K before they come into contact.
194 citations
TL;DR: An explicit quark model, based on a mean field description of nonoverlapping nucleon bags bound by the self-consistent exchange of σ, ω and ϱ mesons, is used to investigate the properties of both nuclear and neutron matter.
192 citations
TL;DR: In this paper, the authors investigated the possibility of kaon condensation in the dense interior of neutron stars through the s-wave interaction of kaons with nucleons and established the conditions under which kaon condensed cores undergo a transition to quark matter containing strange quarks.
178 citations
TL;DR: In this paper, hyperon-nucleon interaction models A and B are presented, in which the explicit energy-dependence of the original models A, B of the Julich group is removed in order to simplify the application in nuclear structure calculations.
158 citations
TL;DR: The double-folding model is generalized for the calculation of nucleus-nucleus potential using the new version of the density-dependent M3Y interaction which reproduces consistently the equilibrium density and binding energy of the normal nuclear matter as well as the density and energy dependence of the nucleon optical potential.
Abstract: The double-folding model is generalized for the calculation of nucleus-nucleus potential using the new version of the density-dependent M3Y interaction which reproduces consistently the equilibrium density and binding energy of the normal nuclear matter as well as the density and energy dependence of the nucleon optical potential. The exchange part of the heavy-ion optical potential is evaluated within a local density formalism, using the finite-range exchange components of the same interaction. The model is used successfully to describe the elastic $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ scattering data at low and medium energies. The influence of different density-dependent parameters (which determine different nuclear equations of state) on the description of heavy-ion scattering is also discussed.
141 citations
TL;DR: The temperature dependence of the coefficients in the semi-empirical mass formula has been determined from a least squares fit to the canonical ensemble average of the excitation energy for nuclei throughout the periodic table.
132 citations
TL;DR: The difference between proton- proton and neutron-proton cross sections is demonstrated and the need to distinguish carefully between the two cases is pointed out.
Abstract: We derive in-medium proton-proton cross sections in a microscopic model based upon the Bonn nucleon-nucleon potential and the Dirac-Brueckner approach for nuclear matter. We demonstrate the difference between proton-proton and neutron-proton cross sections and point out the need to distinguish carefully between the two cases. We also find substantial differences between our in-medium cross sections and phenomenological parametrizations that are commonly used in heavy-ion reactions.
118 citations
TL;DR: In this article, the scattering of antikaons with nucleons in the nuclear environment was studied and it was shown that the mass of the Λ (1405) is shifted upwards in energy due to the Pauli blocking of intermediate states.
TL;DR: In this article, the scattering of antikaons with nucleons is studied in the nuclear environment and it is shown that due to the Pauli blocking of intermediate states, the mass of the Lambda (1405)$ is shifted upwards in energy, above the $K^-$ proton threshold and and its width is somewhat broadened.
Abstract: The scattering of antikaons with nucleons is studied in the nuclear environment. Describing the $\lam$ as a $K^-$ proton bound state, we find, that due to the Pauli blocking of intermediate states, the mass of the $\Lambda (1405)$ is shifted upwards in energy, above the $K^-$ proton threshold and and its width is somewhat broadened. As a consequence the s-wave $K^-$--nucleon scattering length turns attractive at finite nucleon density ($\rho \geq 0.25 \rho_0$) leading to a mean field potential for the $K^-$ of about $\sim -100 \, \rm MeV$ in nuclear matter at ground state density. Consequences for Heavy Ion collisions and possible experimental checks for the structure of the $\lam$ are discussed. (Figures will be sent on request)
TL;DR: In this article, the mass of the ω-meson decreases in nuclear medium using the Walecka model and the physical origin of the decrease is a reduction of the wave function renormalization constant induced by the ϱNN tensor coupling.
TL;DR: In this article, a set of coupled relativistic transport equations for nucleons, antinucleons, scalar and vector mesons is derived in a systematic way by means of the contour Green function technique.
TL;DR: In this paper, the general structure of the hadronic tensor required to describe deep-inelastic scattering from an off-shell nucleon within a covariant formalism was derived.
Abstract: We derive the general structure of the hadronic tensor required to describe deep-inelastic scattering from an off-shell nucleon within a covariant formalism. Of the large number of possible off-shell structure functions we find that only three contribute in the Bjorken limit. In our approach the usual ambiguities encountered when discussing problems related to off shellness in deep-inelastic scattering are not present. The formulation therefore provides a clear framework within which one can discuss the various approximations and assumptions which have been used in earlier work. As examples, we investigate scattering from the deuteron, nuclear matter, and dressed nucleons. The results of the full calculation are compared with those where various aspects of the off-shell structure are neglected, as well as with those of the convolution model.
TL;DR: In this paper, a comprehensive investigation of sub-threshold and threshold kaon production in the framework of the QMD model is presented, which shows that the kaon yield depends strongly on the nuclear equation of state (EOS) and subthreshold kaon experiments may offer the up to now best possibility to determine this yet unknown property of nuclear matter.
TL;DR: An increasing number of physicists are investigating nuclear collisions at relativistic energies, such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory as discussed by the authors.
Abstract: An increasing number of physicists are investigating nuclear collisions at relativistic energies. (See figure 1.) Accelerators completely devoted to the study of these collisions (such as the Relativistic Heavy Ion Collider at Brookhaven National Laboratory) are under construction. So are hadron colliders (such as the Large Hadron Collider at CERN), which can also be used to accelerate heavy ions. The aim of these projects is to study what happens to nuclear matter at high pressures and temperatures. The expectation is that such experiments will access information that can test important predictions of quantum chromodynamics—for example, a nuclear matter transition from a mixture of quarks and gluons to hadrons, as occurred in the first moments of the universe according to the Big Bang theory.
TL;DR: Partial restoration in nuclear matter of the chiral symmetry of QCD is discussed together with some of its possible signals in this article, where estimates of corrections to the leading, linear dependence of the quark condensate are found to be small, implying a significant reduction of that condenate in matter.
Abstract: Partial restoration in nuclear matter of the chiral symmetry of QCD is discussed together with some of its possible signals. Estimates of corrections to the leading, linear dependence of the quark condensate are found to be small, implying a significant reduction of that condensate in matter. The importance of the pion cloud for the scalar quark density of a single nucleon indicates a close connection between chiral symmetry restoration and the attractive two-pion exchange interaction between nucleons. This force is sufficiently long-ranged that nucleons in nuclear matter will feel a significant degree of symmetry restoration despite the strong correlations between them. Expected consequences of this include reductions in hadron masses and decay constants. Various signals of these effects are discussed, in particular the enhancement of the axial charge of a nucleon in matter.
TL;DR: In this paper, anomalous nuclear enhancement in the photoproduction of jets as a higher-twist process in perturbative QCD was analyzed and a physical interpretation of the nuclear enhancement as a measure of the average net transverse color force on an off-shell parton moving through nuclear matter was given.
Abstract: We analyze anomalous nuclear enhancement in the photoproduction of jets as a higher-twist process in perturbative QCD. We use the Fermilab E683 data on dijet momentum imbalance to estimate the size of the relevant twist-4 parton distributions. We find that twist-4 matrix elements are of the order of 0.05-0.1 ${\mathrm{GeV}}^{2}$ times typical twist-2 parton distributions. We discuss a physical interpretation of the nuclear enhancement as a measure of the average net transverse color force on an off-shell parton moving through nuclear matter, and give an order-of-magnitude estimate for the typical squared transverse field strengths encountered by a fast moving parton.
TL;DR: In this paper, the scale invariant term which leads to an omega meson mass, after symmetry breaking, is strongly favored to be of the form ω μ ω φ 2 by the bulk properties of nuclei; they also rather strongly constrain the other parameters.
TL;DR: The Boltzmann-Uehling-Uhlenbeck model is used to simulate the dynamical evolution of heavy-ion collisions and to ocmpare the effects of two parametrizations of the momentum-dependent nuclear mean field that have identical properties in cold nuclear matter.
Abstract: We use the Boltzmann-Uehling-Uhlenbeck model to simulate the dynamical evolution of heavy-ion collisions and to ocmpare the effects of two parametrizations of the momentum-dependent nuclear mean field that have identical properties in cold nuclear matter. We compare with recent data on nuclear flow, as characterized by transverse momentum distributions and flow ([ital F]) variables for symmetric and asymmetric systems. We find that the precise functional dependence of the nuclear mean field on the particle momentum is important. With our approach, we also confirm that the difference between symmetric and asymmetric systems can be used to pin down the density and momentum dependence of the nuclear self-consistent one-body potential, independently. All the data can be reproduced very well with a momentum-dependent interaction with an equilibrium nuclear matter compressibility [ital K]=210 MeV.
TL;DR: It is found that combustion is possible for free neutron, Bethe-Johnson, and Lattimer-Ravenhall neutron matter but not for Walecka neutron matter, and the conditions for the deflagration to detonation transition are addressed, showing that in a pipe some of them are satisfied, strongly suggesting that the actual combustion mode should be detonation.
Abstract: We study the properties of the combustion of pure neutron matter into strange matter in the framework of relativistic hydrodynamical theory of combustion. Because of the uncertainties in the actual properties of neutron matter, we employ the free neutron, Bethe-Johnson, Lattimer-Ravenhall, and Walecka equations of state and for strange matter we adopt the MIT bag model approximation. We find that combustion is possible for free neutron, Bethe-Johnson, and Lattimer-Ravenhall neutron matter but not for Walecka neutron matter. We interpret these results using a simple polytropic approximation showing that there exists a general flammability condition. We also study the burning of neutron matter into strange matter in a pipe showing that hydrodynamics demands flames faster than predicted by kinetics by several orders of magnitude, implying that the flame must be turbulent. Also the conditions for the deflagration to detonation transition are addressed, showing that in a pipe some of them are satisfied, strongly suggesting that the actual combustion mode should be detonation.
TL;DR: In this paper, temperature-dependent mean field potentials of nucleons are obtained by solving the Bethe-Goldstone equation for a realistic force in nuclear matter at finite temperature.
TL;DR: This article calculates the characteristic time of the exponential growing of fluctuations and the diffusion coefficients associated to the unstable modes, in the framework of the Boltzmann-Langevin theory, using a semiclassical stochastic mean-field approach to make realistic 3D calculations feasible.
Abstract: In this article, we consider a semiclassical stochastic mean-field approach. In the case of unstable infinite nuclear matter, we calculate the characteristic time of the exponential growing of fluctuations and the diffusion coefficients associated to the unstable modes, in the framework of the Boltzmann-Langevin theory. These two quantities are essential to describe the dynamics of fluctuations and instabilities since, in the unstable regions, the evolution of the system will be dominated by the amplification of fluctuations. In order to make realistic 3D calculations feasible, we suggest to replace the complicated Boltzmann-Langevin theory by a simpler stochastic mean-field approach corresponding to a standard Boltzmann evolution, complemented by a simple noise chosen to reproduce the dynamics of the most unstable modes. Finally we explain how to approximately implement this method by simply tuning the noise associated to the use of a finite number of test particles in Boltzman-like calculations.
TL;DR: In this article, the relativistic mean field model was used to study the properties of antikaons and kaons in dense nuclear matter, and it was shown that antikaon condensation may occur in chiral models, only for relatively high values of the nucleon effective mass, m N ∗ /m N > 0.75, and does not occur in models based on one boson exchange underlying K N interactions.
TL;DR: The in-medium nucleon-nucleon cross section is calculated starting from the thermodynamic [ital T] matrix at finite temperatures and an enhancement near the Fermi energy is observed.
Abstract: The in-medium nucleon-nucleon cross section is calculated starting from the thermodynamic [ital T] matrix at finite temperatures. The corresponding Bethe-Salpeter equation is solved using a separable representation of the Paris nucleon-nucleon potential. The energy-dependent in-medium [ital N]-[ital N] cross section at a given density shows a strong temperature dependence. Especially at low temperatures and low total momenta, the in-medium cross section is strongly modified by in-medium effects. In particular, with decreasing temperature an enhancement near the Fermi energy is observed. This enhancement can be discussed as a precursor of the superfluid phase transition in nuclear matter.
TL;DR: The quark and gluon viscosities are calculated in quark-gluon plasmas to leading orders in the coupling constant by including screening and the leading logarithmic order is calculated exactly by a full variational treatment.
Abstract: The quark and gluon viscosities are calculated in quark-gluon plasmas to leading orders in the coupling constant by including screening. For weakly interacting QCD and QED plasmas, dynamical screening of transverse interactions and Debye screening of longitudinal interactions controls the infrared divergences. For strongly interacting plasmas other screening mechanisms taken from lattice calculations are employed. By solving the Boltzmann equation for quarks and gluons including screening, the viscosity is calculated to leading orders in the coupling constant. The leading logarithmic order is calculated exactly by a full variational treatment. The next to leading orders are found to be important for the transport properties of quark-gluon plasmas created in relativistic heavy-ion collisions and the early universe, where the coupling constant is large.
TL;DR: In this paper, the properties of hot asymmetric nuclear matter are investigated in the framework of an extended Brueckner-Bethe-Goldstone theory, using the Paris nucleon-nucleon interaction.
TL;DR: A novel method is presented for introducing fluctuations in one-body dynamics using a Brownian force in the kinetic equations for nuclear matter within the spinodal zone, and promises to provide a practical means for addressing catastrophic nuclear processes.
Abstract: A novel method is presented for introducing fluctuations in one-body dynamics. It consists of employing a Brownian force in the kinetic equations. For nuclear matter within the spinodal zone, the magnitude of the Brownian force can be determined by demanding correspondence with the growth of the most unstable mode, as given by Boltzmann-Langevin simulations. The method is illustrated and tested for idealized two-dimensional matter and promises to provide a practical means for addressing catastrophic nuclear processes.