Investigation of the symmetry energy of nuclear matter using isospin-dependent quantum molecular dynamics

Simulations of infinite nuclear matter at different densities,isospin asymmetries and temperatures are performed using the isospin-dependent quantum molecular dynamics(IQMD)model to study the equation of state and symmetry energy.A rigorous periodic boundary condition is used in the simulations.Symmetry energies are extracted from the binding energies under different conditions and compared to the classical molecular dynamics(CMD)model using the same method.The results show that both models can reproduce the experimental results for the symmetry energies at low densities,but IQMD is more appropriate than CMD for nuclear matter above the saturation density.This indicates that IQMD may be a reliable model for the study of the properties of infinite nuclear matter.

The Brueckner-Hartree-Fock Equation of State for Nuclear Matter and Neutron Skin

The equation of state for nuclear matter is presented within the Brueckner Hartree-Fock （BHF） scheme, by using the realistic Argonne VI8 or Bonn B two-nucleon potentials plus their corresponding microscopic three-nucleon forces. It is then applied to calculate the properties of finite nuclei within a simple liquid-drop model, and we compare the calculated volume, surface, and Coulomb parameters with the empirical ones from the liquid drop model. Nuclear density distributions and charge radii in good agreement with the experimental data are obtained~ and we predict the neutron skin thickness of various nuclei.

A Mean-Field Treatment in Studying Nuclear Matter Through a Thermodynamic Consistent Resummation Scheme

We used the Cornwall, Jackiw and Tomboulis （CJT） resummation scheme to study nuclear matter. In the CJT formalism the meson propagators are treated as the bare propagators and the the higher order loop corrections of the thermodynamic potential are evaluated at the Hartree approximation, while the vacuum fluctuations are ignored. Under these treatments in the CJT formalism we derived exact mean-field theory （MFT） results for the nuclear matter. The results are thermodynamically consistent, and our study indicates that the MFT result is the lowest order resummation result in the CJT resummation scheme. The relation between CJT formalism and MFT is clearly presented through the calculations.

Constraints on Estimation of Radius of Double Pulsar PSR J0737-3039A and Its Neutron Star Nuclear Matter Composition

The aspect of formation and evolution of the recycled pulsar（PSR J0737-3039 A/B） is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram（- diagram） in the double pulsar system. Accepting the spin-down age as a rough estimate（or often an upper limit） of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.

Shear viscosity of nuclear matter

This paper reports my recent study[1]on the shear viscosity of neutron-rich nuclear matter from a relaxation time approach.An isospin- and momentum-dependent interaction is used in the study.Dependence of density,temperature,and isospin asymmetry of nuclear matter on its shear viscosity have been discussed.Similar to the symmetry energy,the symmetry shear viscosity is defined and its density and temperature dependence are studied.

Constraints on the skewness coefficient of symmetric nuclear matter within the nonlinear relativistic mean field model

Within the nonlinear relativistic mean field(NLRMF) model, we show that both the pressure of symmetric nuclear matter at supra-saturation densities and the maximum mass of neutron stars are sensitive to the skewness coefficient, J_0, of symmetric nuclear matter. Using experimental constraints on the pressure of symmetric nuclear matter at supra-saturation densities from flow data in heavy-ion collisions and the astrophysical observation of a large mass neutron star PSR J0348+0432, with the former favoring a smaller J_0 while the latter favors a larger J_0, we extract a constraint of -494 MeV≤J_0≤-10 MeV based on the NL-RMF model. This constraint is compared with the results obtained in other analyses.

Apparent softening of the symmetry energy with the inclusion of non-nucleonic components in nuclear matter

Apparent softening of the symmetry energy with the inclusion of hyperon and quark degrees of freedom is demonstrated by the fact that the phase transition causes the change of the interaction and the suppression of nucleon fractions.The demonstration is fulfilled in the relativistic mean-field model.

Incompressibility of Nuclear Matter in a Quark-Meson Coupling Model

The quark meson coupling model is used to investigate the correlation between thenuclear incompressibility K and the third order derivitive K′ of the nuclear matter saturationcurve,the temperature and entropy dependence of the nuclear

Three—Body Force Effects on EOS of Asymmetric Nuclear Matter and Proton Fraction in Neutron Star Matter

The three-body force effects on the equation of state and its iso-spin dependence of asymmetric nuclearmatter and on the proton fraction in neutron star matter have been investigated within Brueckner-Hartree-Fock approachby using a microscopic three-body force. It is shown that, even in the presence of the three-body force, the empiricalparabolic law of the energy per nucleon vs. isospin asymmetry β＝ ( N - Z) /A is fulfilled in the whole asymmetry range0≤β≤1 and also up to high density. The three-body force provides a strong enhancement of symmetry energy at highdensity in agreement with relativistic approaches. It also shows that the three-body force leads to a much more rapidincreasing of symmetry energy with density in relatively high density region and to a much lower threshold density forthe direct URCA process to occur in a neutron star as compared to the predictions adopting only pure two-body force.

Nucleon ~3pF_2 Superfluid Pairing Gap in Asymmetry Nuclear Matter

3 PF 2 中子和质子的超级流动性被采用 Argonne V14 和 Argonne V18 核子核子在 Brueckner Hartree Fock 途径和 BCS 理论以内在 isospin 不对称的原子物质调查相互作用。我们发现那在 3 采用 AV14 相互作用预言的 PF 2 隧道比由 AV18 相互作用的那些大得多。作为 isospin 不对称现象增加，中子 3 超级流动性被发现很快增加的 PF 2 ，而一个人生产到的质子减少并且可以甚至消失在足够高的不对称现象。作为后果，中子 3 PF 2 超级流动性比在高不对称现象和它的支配的质子强壮得多质子在稠密的充满中子的物质的。

Microscopic Three-Body Force Effect on Nucleon-Nucleon Cross Sections in Symmetric Nuclear Matter

We provide a microscopic calculation of neutron-proton and proton-proton cross sections in symmetricnuclear matter at various densities,using the Brueckner-Hartree-Fock approximation scheme with the Argonne V_(14)potential including the contribution of microscopic three-body force.We investigate separately the effects of three-bodyforce on the effective mass and on the scattering amplitude.In the present calculation,the rearrangement contributionof three-body force is considered,which will reduce the neutron and proton effective mass,and depress the amplitudeof cross section.The effect of three body force is shown to be repulsive,especially in high densities and large momenta,which will suppress the cross section markedly.

Isovector Scalar Field Effects in Asymmetric Nuclear Matter

包括 isovector 数量 δ-field，联合常数的核子介子的密度依赖者 parametrization 模型被用于不对称的原子物质。状态(曙光女神) 和中子星性质的原子方程在相对论的 Lagrangian 密度被学习，用相对论的吝啬的领域(RMF ) 强子理论。在不变的联合计划的 δ-field 在稠密的充满中子的物质并且到质子和中子的明确的切开导致更大的排斥，这被知道有效群众，最后影响中子星的稳定性。我们使用核子介子政变石楠的密度依赖者模型学习中子星物质的性质并且再考在不对称的原子物质的 δ-field 效果。我们中子星的稳定性条件有关系的计算表演能在联合常数的密度依赖者模型在 δ-meson 的存在被改进。原子物质的曙光女神强烈取决于相互作用的密度依赖。

Some Properties of π Meson in Nuclear Matter with Finite Density

In the GCM we study some properties of π meson as the Goldstone bosons in a nuclear matter with finite density.Using the effective action in a nuclear matter,we calculate the decay constant and π mass as functions of the chemical potential.The relation between the chemical potential and the density of a nuclear matter is firstly given here.We find that fπ and mπ monotonously decrease as nuclear matter density increases.The result is consistent with the usual assumption that the chiral symmetry is gradually restored as the density of a nuclear matter increases.

Spin—Polarized States of Nuclear Matter

The equations of state of spin-polarized nuclear matter and pure neutron matter are studied in theframework of the Brueckner-Hartree-Fock theory including a three-body force. The energy per nucleon E A (δ) calculatedin the full range of spin polarization δ = (ρ↑ - ρ↓)/ρ for symmetric nuclear matter and pure neutron matter fulfills aparabolic law. In both the cases the spin-symmetry energy is calculated as a function of the baryonic density alongwith the related quantities such as the magnetic susceptibility and the Landau parameter Go. The main effect of thethree-body force is to strongly reduce the degenerate Fermi gas magnetic susceptibility even more than the value withonly two-body force. The equation of state is monotonically increasing with the density for all spin-aligned configurationsstudied here so that no any signature is found for a spontaneous transition to a ferromagnetic state.

Finite Temperature Asymmetric Nuclear Matter Using Pion Dressing

We study the asymmetric nuclear matter in a nonperturvative manner at finite temperatures using thermofield dynamics method. The nucleon-meson interaction is taken to examine the binding energy (EB), pressure (P) for various proton fractions.

Nucleon in Nuclear Matter

The modification of the properties of nucleon in nuclear medium has been investigated in the context of flux tube model. A nucleon has been described as diquark-quark system connected by flux tube and quasi particle diquark model has been used to describe the diquak constituting the nucleon. The modification of incompressiblity, the Roper resonance etc in the nuclear medium have been investigated. The results are compared with recent experimental and theoretical predictions. Some interesting observations are made.

The Equation of State of Nuclear Matter and Neutron Stars Properties

The equation of state (EOS) of symmetric nuclear and pure neutron matter has been investigated extensively by adopting the non-relativistic Brueckner-Hartree-Fock (BHF). For more comparison, the extended BHF approaches using the self-consistent Green’s function approach or by including a three-body force will be done. The EOS will be studied for different approaches at zero temperature. We can calculate the total mass and radius of neutron stars using various equations of state. A comparison with relativistic BHF calculations will be done. Relativistic effects are known to be important at high densities, giving an increased repulsion. This leads to a stiffer EOS compared to the EOS derived with a non-relativistic approach.

Chiral σ-ω Model Study of Hot Dense Nuclear Matter

The hot dense nuclear matter is studied in the chiral σ-ω model in theformalism of thermo-field dynamics.The binding energy,pressure and effective mass ofnucleon are calculated in the level of one-loop vaccum quantum fluctuation.The tem-perature effect is found very large at high temperature and the pressure can not reachsaturation as a function of nuclear density.

Three-body force effect on the properties of nuclear matter under the gap and continuous choices within the BHF approach

We have calculated and compared the three-body force effects on the properties of nuclear matter under the gap and continuous choices for the self-consistent auxiliary potential within the Brueckner-Hartree-Fock approach by adopting the Argonne Vls and the Bonn B two-body potentials plus a microscopic three-body force （TBF）. The TBF provides a strong repulsive effect on the equation of state of nuclear matter at high densities for both the gap and continuous choices. The saturation point turns continuous choice is adopted. In addition, the dependence self-consistent auxiliary potential is discussed. out to be much closer to the empirical value when the of the calculated symmetry energy upon the choice of the