Anisotropic pressure in dense neutron matter under the presence of a strong magnetic field

Dense neutron matter with recently developed BSk19 and BSk21 Skyrme effective forces is considered in magnetic fields up to ¹⁰²⁰ G at zero temperature. The breaking of the rotational symmetry by the magnetic field leads to the differentiation between the pressures along and perpendicular to the field direction which becomes significant in the fields H>Hth∼¹⁰¹⁸ G. The longitudinal pressure vanishes in the critical field ¹⁰¹⁸<Hc?¹⁰¹⁹ G, resulting in the longitudinal instability of neutron matter. For the Skyrme force fitted to the stiffer underlying equation of state (BSk21 vs. BSk19) the threshold Hth and critical Hc magnetic fields become larger. The longitudinal and transverse pressures as well as the anisotropic equation of state of neutron matter are determined under the conditions relevant for the cores of magnetars.     

Vacuum fluctuation effects on hyperonic neutron star matter

The vacuum fluctuation （VF） effects on the properties of the hyperonic neutron star matter are investigated in the framework of the relativistic mean field （RMF） theory. The VF corrections result in the density dependence of in-medium baryon and meson masses. We compare our results obtained by adopting three kinds of meson-hyperon couplings. The introduction of both hyperons and VF corrections softens the equation of state （EoS） for the hyperonic neutron star matter and hence reduces hyperonic neutron star masses. The presence of the δ field enlarges the masses and radii of hyperonic neutron stars. Taking into account the uncertainty of meson-hyperon couplings, the obtained maximum masses of hyperonic neutron stars are in the range of 1.33M⊙-1.55M⊙.     

Infinite matter properties and zero-range limit of non-relativistic finite-range interactions

We discuss some infinite matter properties of two finite-range interactions widely used for nuclear structure calculations, namely Gogny and M3Y interactions. We show that some useful informations can be deduced for the central, tensor and spin–orbit terms from the spin–isospin channels and the partial wave decomposition of the symmetric nuclear matter equation of state. We show in particular that the central part of the Gogny interaction should benefit from the introduction of a third Gaussian and the tensor parameters of both interactions can be deduced from special combinations of partial waves. We also discuss the fact that the spin–orbit of the M3Y interaction is not compatible with local gauge invariance. Finally, we show that the zero-range limit of both families of interactions coincides with the specific form of the zero-range Skyrme interaction extended to higher momentum orders and we emphasize from this analogy its benefits.     

凝聚态物质状态方程的一个数值模型

建立了凝聚态物质的一个三项式状态方程：以Faussurier平均原子模型为基础计算电子热压和电子热能;以Cowan模型为基础计算离子热压和离子热能;用基于实验数据的半经验拟合公式计算物质的冷压和冷能。用实验数据检验了用平均原子模型计算的平均电离度。将状态方程与Hugoniot关系式相结合,计算了Be和Al的冲击绝热曲线,结果充分地展现出电子在高温、高密度条件下的壳层结构效应。     

Dark energy interacting with dark matter and a third fluid: Possible EoS for this component

A cosmological model of dark energy interacting with dark matter and another general component of the universe is considered. The equations for the coincidence parameters r and s, which represent the ratios between dark energy and dark matter and the other cosmic fluid respectively, are analyzed in terms of the stability of stationary solutions. The obtained general results allow to shed some light on the equations of state of the three interacting fluids, due to the constraints imposed by the stability of the solutions. We found that for an interaction proportional to the sum of the dark energy density and the third fluid density, the hypothetical fluid must have positive pressure, which leads naturally to a cosmological scenario with radiation, unparticle or even some form of warm dark matter as the third interacting fluid.     

Equation of state for QCD matter in a quasiparticle model

A phenomenological QCD quasiparticle model provides a means to map lattice QCD results to regions, relevant for a variety of heavy-ion collision experiments at larger baryon density. We report on the effects of collectives modes and damping on the equation of state.     

强磁场中氢分子离子H_2~ 反键态能级的绝热变分计算

采用绝热变分近似方法 ,计算了均匀强磁场 (0 .5≤β≤ 10 0 0 )中H 2 的Δu,Φg,Γu,Hg 态 (无外磁场或外磁场较弱时为反键态 )的能级及原子核间的平衡距离 ,并与前人的结果进行了比较。     

Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.     

Observations of neutron stars and the equation of state of matter at high densities

We summarize the constraints on the equation of state of high-density nuclear matter derived from neutron star observations. The most stringent constraints are provided by the largest mass, the largest radius, the highest rotational frequency, and the maximum surface gravity observed for neutron stars. The combination of these constraints allows only nuclear equations of state which are quite stiff.     

Information theoretical methods as discerning quantifiers of the equations of state of neutron stars

In this work we use the statistical measures of information entropy, disequilibrium and complexity to discriminate different approaches and parametrizations for different equations of state for quark stars. We confirm the usefulness of such quantities to quantify the role of interactions in such stars. We find that within this approach, a quark matter equation of state such as SU(2) NJL with vectorial coupling and phase transition is slightly favoured and deserves deeper studies.     

Charmonia and bottomonia in asymmetric magnetized hot nuclear matter

We investigate the mass-shift of P-wave charmonium(χ_(c0),χ_(c1)),and S and P-wave bottomonium(η_b,■,χ_(b0),and χ_(b1)) states in magnetized hot asymmetric nuclear matter using the unification of QCD sum rules(QCDSR)and the chiral S U(3) model.Within QCDSR,we use two approaches,i.e.,the moment sum rule and the Borel sum rule.The magnetic field induced scalar gluon condensate α_s/πG_(μν)~aG~(aμν) and the twist-2 gluon operatorα_s/πG_(μσ)~aG~a ν~σcalculated in the chiral S U(3) model are utilised in QCD sum rules to calculate the in-medium mass-shift of the above mesons.The attractive mass-shift of these mesons is observed,which is more sensitive to magnetic field in the high density regime for charmonium,however less so for bottomonium.These results may be helpful to understand the decay of higher quarkonium states to the lower quarkonium states in asymmetric heavy ion collision experiments.     

Incompressibility of strange matter

Strange stars (ReSS) calculated from a realistic equation of state (EOS), that incorporate chiral symmetry restoration as well as deconfinement at high density [Phys. Lett. B 438 (1998) 123; Phys. Lett. B 447 (1999) 352, Addendum; Phys. Lett. B 467 (1999) 303, Erratum; Indian J. Phys. B 73 (1999) 377] show compact objects in the mass radius curve. We compare our calculations of incompressibility for this EOS with that of nuclear matter. One of the nuclear matter EOS has a continuous transition to ud-matter at about five times normal density. Another nuclear matter EOS incorporates density dependent coupling constants. From a look at the consequent velocity of sound, it is found that the transition to ud-matter seems necessary.     

Modern trends in the development of position sensitive neutron detectors for condensed matter research

Different types of neutron scattering experiment for the study of condensed matter properties pose specific and often contradictory requirements for detector characteristics. There is no single type of detector which satisfies all the criteria. Therefore, compromise is inevitable and some of the characteristics are trade off in favour of others. Present report gives an overview of detector systems presently operating at the leading neutron scattering facilities as well as some development work around the globe.      

Polarized neutron imaging: A spin-echo approach

Polarized neutron imaging has recently been introduced as an efficient method to three-dimensionally visualize and measure magnetic fields even in the bulk of massive objects. Here we introduce a spin-echo approach for polarized neutron imaging, which has the potential to overcome some drawbacks of the first attempts, namely to deal with strong fields, arbitrary field directions and quantification. Furthermore our novel approach increases the efficiency of quantitative studies due to relaxed monochromatisation requirements for spin-echo neutron imaging and with respect to additional information available in the recorded images, which allows for straightforward quantification in many cases.     

Higher order bulk characteristic parameters of asymmetric nuclear matter

The bulk parameters characterizing the energy of symmetric nuclear matter and the symmetry energy defined at normal nuclear density ρ0 provide important information on the equation of state (EOS) of isospin asymmetric nuclear matter. While significant progress has been made in determining some lower order bulk characteristic parameters, such as the energy E0(ρ0) and incompress ibility K0 of symmetric nuclear matter as well as the symmetry energy Esym(ρ0) and its slope parameter L, yet the higher order bulk ...     

Parametrization of light nuclei quasiparticle energy shifts and composition of warm and dense nuclear matter

Correlations and the formation of bound states (nuclei) are essential for the properties of nuclear matter in equilibrium as well as in nonequilibrium. In a quantum statistical approach, quasiparticle energies are obtained for the light elements that reflect the influence of the medium. We present analytical fits for the quasiparticle energy shifts of light nuclei that can be used in various applications. This is a prerequisite for the investigation of warm and dense matter that reproduces the nuclear statistical equilibrium and virial expansions in the low-density limit as well as relativistic mean field and Brueckner Hartree-Fock approaches near saturation density.     

Linear and nonlinear excitations in warm dense matter

Small and large amplitude linear and nonlinear ion acoustic and Langmuir waves are investigated for plasma with the generalized equation of state (EoS). This EoS covers a wide range of energy-density conditions from dilute classical regime up to the relativistically degenerate matter. Investigation shows that the linear dispersion and localized excitations of ion acoustic waves are significantly affected by the plasma parameters. It is also found that the criterion for ordinary soliton existence is significantly different for fully degenerate and nondegenerate plasma regimes with given electron temperature. In the nondegenerate regime, bright solitons form only for Mach numbers above a critical value which is only a function of the fluid temperature.