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δ介子对确定K介子有效质量的影响 总被引:1,自引:1,他引:0
运用密度相关的平均场理论,分析了耦合常数随密度的变化及其对核子有效质量的影响.尤其引入δ介子后,质子和中子的同位旋效应得到体现,使非对称核物质中质子和中子的有效质量出现差别,从而对标量密度产生影响.利用含δ介子密度相关的相对论平均场理论,计算了在对称和非对称核物质中标量密度ρS和矢量密度ρB的关系,并由此研究了K介子有效质量随核物质密度的变化,分析了密度相关的耦合常数以及核物质非对称参数对K介子有效质量产生影响的大小,并与在耦合常数不依赖于核物质密度的情况下进行了比较. 相似文献
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本文对比分析了目前用于研究K介子产生与演化的不同动力学模型中,高温高密核物质中K+介子和K-介子的等效质量和它所感受到的平均场.所得结果显示:在关于K介子的一般的平均场理论中,所定义的K+介子的等效质量随着核物质密度的增大而增加, K-介子的等效质量随着核物质密度的增大而减小;但在K介子演化的协变动力学模型中,所采用的K+介子和K-介子等效质量是随着核物质密度的增大都是减小的
关键词:
高密核物质
K介子
等效质量
核子运动 相似文献
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在密度相关的相对论平均场近似下,研究了核介质密度对σ,ω,ρ,π介子有效质量的影响并与线性Walecka模型、非线性Walecka模型及TW模型的计算相比较,结果表明不同模型参数下的介子有效质量的变化不会有太大的差别.在低密度区域内,介子有效质量随核物质密度的增大而减小,而在密度较高时,σ,π介子的有效质量随核物质密度的增大而增大,ω,ρ介子的有效质量随核物质密度的增大其减小趋于平缓.不对称系数α对介子有效质量的影响很小.在TM1参数中σ介子的非线性自相互作用项以及多体耦合项(σπ)2对于π介子有效质量的影响是重要的. 相似文献
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The properties of symmetric nuclear matter are investigated in a phenomenological non-linear relativistic field theory of nuclear matter. A mean field approximation is made. We find that the equation of state over a considerable density range is determined by the nuclear matter compressibility modulus. A family of equations of state is considered that fit all known bulk properties of nuclear matter, including the energy dependence of the optical potential. The importance of non-Yukawa type nuclear interactions is discussed. 相似文献
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Pion condensation has not previously been investigated in a theory that accounts for the known bulk properties of nuclear matter, its saturation energy and density and compressibility. We have formulated and solved self-consistently, in the mean field approximation, a relativistic field theory that possesses a condensate solution and reproduces the correct bulk properties of nuclear matter. The theory is solved in its relativistically covariant form for a general class of space-time dependent pion condensates. Self-consistency and compatibility with bulk properties of nuclear matter turn out to be very stringent conditions on the existence and energy of the condensate, but they do allow a weak condensate energy to develop. The spin-isospin density oscillations, on the other hand, can be large. It is encouraging, as concerns the possible existence of new phases of nuclear matter, that this is so, unlike the Lee-Wick density isomer, that appears to be incompatible with nuclear matter properties. 相似文献
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A relativistic mean field model is used to study the ground-state properties of neutron-rich nuclei in Ca isotopes. An additional isoscalar and isovector nonlinear coupling has been introduced in the relativistic mean field model, which could soften the symmetry energy, while keep the agreement with the experimental data. The sensitivity of proton and neutron density distributions and single particle states in Ca isotopes to the additional isoscalarisovector nonlinear coupling term is investigated. We found that the binding energies, the density distributions of single particle levels are strongly correlated with the density dependence of the symmetric energy in nuclear matter. 相似文献
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We study the spinodal instabilities of asymmetric nuclear matter at finite temperature within the microscopic Brueckner–Hartree–Fock (BHF) approximation using the realistic Argonne V18 nucleon–nucleon potential plus a three-body force of Urbana type. Our results are compared with those obtained with the Skyrme force SLy230a and the relativistic mean field models NL3 and TW. We find that BHF predicts a larger spinodal region. This result is a direct consequence of the fact that our Brueckner calculation predicts a larger critical temperature and saturation density of symmetric nuclear matter than the Skyrme and relativistic mean field ones. We find that the instability is always dominated by total density fluctuations, in agreement with previous results of other authors. We study also the restoration of the isospin symmetry in the liquid phase, i.e., the so-called isospin distillation or fragmentation effect, finding that its efficiency increases with increasing proton fraction and decreases as temperature and density increase. In general, we find that the Brueckner results are comparable to those obtained with the Skyrme and the relativistic mean field models, although the restoration of isospin symmetry is not so efficient in this case. 相似文献
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A relativistic Hartree-Fock mean field approximation is investigated in a model in which the nucléon field interacts with scalar and vector meson fields. The Hartree-Fock potential felt by individual nucléons enters in a relativistic Dirac single-particle equation. It is shown that in the case of symmetric nuclear matter one can always find a potential which is fully equivalent to the most general mean field and which is only the sum of a Lorentz scalar, of one component of a Lorentz tensor and of the fourth component of a Lorentz vector. A non-relativistic potential is derived which yields exactly the same single-particle energies and elastic scattering phase shifts as the relativistic Hartree-Fock potential. Analytical results are presented in the case of nuclear matter. A local density approximation is constructed which enables one to consider finite nuclei. The input parameters of the model can be chosen in such a way that the empirical saturation properties of nuclear matter are well reproduced. Good agreement is obtained between the calculated non-relativistic potential and the empirical value of the real part of the optical-model potential at low and at intermediate energy. At intermediate energy, the wine-bottle bottom shape which had previously been found for the potential in the framework of the relativistic Hartree approximation is maintained when the Fock contribution is included. 相似文献
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在Walecka模型的基础上,应用热动力学理论和Dirac-Bruckner-Hartree-Fock方法,研究了有限温度不同密度下核子相对论微观光学势及其相应的薛定谔等效势和平均自由程.计算结果表明,核子薛定谔等效势和平均自由程对核密度的依赖相当敏感,当核密度增大时对核密度的依赖变得更为敏感. 相似文献
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研究和详细地比较了RMF理论中不同的有效相互作用强度的密度依赖性, 并且讨论了这种密度依赖性对于核物质和中子星性质的影响. 对于核物质, 不同的参数组给出的对称核物质的饱和点非常接近, 基本都在经验值的范围内. 对于中子星, 考虑超子后不同参数组给出的质量极限的范围为1.52—2.06 M☉, 半径为10.24—11.38 km.The density dependencies of various effective interaction strengths in the relativistic mean field and their influences on the properties of nuclear matter and neutron stars are studied and carefully compared. The differences of saturation properties given by various effective interactions are subtle in symmetric nuclear matter. The Oppenheimer Volkoff mass limits of neutron stars calculated from different equations of state are 1.52—2.06 M☉, and the radii are 10.24—11.38 km with hyperons included. 相似文献
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K.-H. Müller 《Nuclear Physics A》1981,372(3):459-482
We treat the dynamics of colliding nuclear slabs in a relativistic quantum field theory by using the relativistic mean field approximation. Starting from Walecka's lagrangian, the nucleons are represented by single-particle spinors determined by a Dirac equation that contains a repulsive mean vector meson field and an attractive mean scalar meson field. Both fields satisfy Klein-Gordon equations whose source terms are again determined by the nucleon spinors. The two equal nuclear slabs are translationally invariant in two transverse dimensions and consist of spin and isospin symmetric nuclear matter. By specification of appropriate initial conditions for the collision, we numerically solve the system of coupled Dirac and Klein-Gordon equations for lab energies per nucleon up to 420 MeV. For small energies the results are similar to TDHF results. The time dependence of the density distribution, the mean meson fields, and the damping of the collision are studied. At the highest bombarding energy retardation effects are taken into account. 相似文献
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A. Delfino Jishnu Dey Mira Dey M. Malheiro 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):507-514
The models of translationally invariant infinite nuclear matter in the relativistic mean field models are very interesting and simple, since the nucleon can connect only to a constant vector and scalar meson field. Can one connect these to the complicated phase transitions of QCD? For an affirmative answer to this question, one must consider models where the coupling contstants to the scalar and vector fields depend on density in a nonlinear way, since as such the models are not explicitly chirally invariant. Once this is ensured, indeed one can derive a quark condensate indirectly from the energy density of nuclear matter which goes to zero at large density and temperature. The change to zero condensate indicates a smooth phase transition. 相似文献