【作者】 金猛；

【导师】 李家荣；

【作者基本信息】 华中师范大学 ， 理论物理， 2004， 博士

【摘要】 核物质是由大量核子组成的多粒子系统。对核物质性质的主要研究方法是相对论核多体理论。这一理论从系统成分粒子的动力学出发，按统计热力学的方法来讨论体系的性质。本文主要基于相对论量子强子动力学(QHD)模型，在温度场论的框架下，讨论了热密核物质的若干性质。 在文章的前一部分，我们仔细研究了QHD-Ⅰ模型中核子有效质量(M*)随温度(T)化学势(μ)的变化情况，特别是其在高温区的行为，发现有效质量的自洽方程在高温区存在多个解。经过分析我们判断此处可能存在一个汽液相变。随后我们给出了该温度化学势区域系统压强对数密度的变化曲线，证实了这一相变的存在。同时我们得出结论，核子有效质量的多解必然预示着核物质的汽液相变。为了证明这一结论，我们以QHD-Ⅰ模型中众所周知的低温区汽液相变为例。经研究发现在低温相变发生的温度化学势区域，核子有效质量果然存在多解的现象。由于我们所讨论的模型中并不涉及夸克胶子自由度，因此QHD-Ⅰ模型中高温区的新的相变仍然是强子层次上的相变。在文章中我们还以QHD-Ⅱ模型为例，同样发现了高温区的相变。 一般来讲，所有的热力学相变都会有其对应的动力学背景。我们类比原子分子系统中分析相变的动力学方法，通过计算核物质中介子的Debye屏蔽质量，给出了核子核子相互作用势在不同温度和化学势下的变化行为。发现相互作用势阱消失时的温度和化学势恰好对应着由P-ρ相图给出的相变临界温度和化学势。这样就从核子核子相互作用势阱由于温度密度效应而消失，核子束缚被解体方面给了相变一个动力学解释。 最近，关于强作用介质中场的性质的研究引起了人们的广泛注意。主要是因为在介质中的场与其在自由空间中有着非常不同的性质。一方面，有许多作者提出了准粒子或激发模式的概念来描述这种热密环境中粒子的行为。大量工作来讨论介质中玻色子和费米子的性质，如色散关系、有效质量、衰变宽度以及阻尼等。另一方面，介质中场性质的改变也可由两个独立的物理量-介电函数和磁导率-来标志。这两个物理量从介质中电场和磁场变形的角度给出了热密介质系统介质效应的最直观描写。 介电函数和磁导率最初是在讨论经典电动力学的介质效应时提出来的，后来又被用于讨论量子电动力学的介质行为。介电函数和磁导率定义为介质中电场和磁场相对于真空中的变化。注意到QCD中的场张量也可类比QED中的场张量分解为电分量和磁分量，因此人们也相应地引入了色介电函数和色导率来讨论QCD介质的色介电性质。同样，为了讨论核物质中介子场和真空中介子场的区别，人们也可以引入核物质蕃博士学位论文DOCI，O凡从DISSERfATION5 介质的“介电”函数。然而，几乎所有现有的工作都只注重核物质介电函数在讨论其 它物理性质时的应用，而没有涉及到介电函数本身的性质.在本文的后一部分，我们 将讨论核物质系统的介电函数的一些特征. 我们先从矢量介子的作用量出发，借助于量子电动力学中推导介电函数的方法， 通过适当的方法处理矢量介子有效作用量中的质量项，得到有质量系统的介电函数表 达式，讨论了介电函数在有限密度下随介子能量的变化曲线.我们发现在介子类空和 类时区域，介电函数对应有两个非平庸结构.通过分析介质中极化核子流产生的机制， 我们分别给出这两个非平庸结构的物理解释.随后我们将这种有效作用量的分析方法 应用到QHD一I模型，考虑到更多的核子流产生机制，在一个完整的核模型框架下讨论 了核物的质介电性质.为了与相对论重离子碰撞和致密星物理相对应，我们分别对高 温低化学势和低温高化学势两种极端情形下的核物质介电函数进行了研究.最后我们 还讨论了核物质中各种极化流产生的机制，以及核介质中独有的混合极化问题。我们 发现由于混合极化的存在，在热密核物质中极化核子流产生的一种新机制，即标量介 子极化可以产生矢量核子流，矢量介子极化可产生标量核子流。同时我们还发现混合 极化不论是对核物质中的极化流还是对介电函数都有不可忽视的贡献。更多还原

【Abstract】 Nuclear matter is a system contains a large number of nucleons. The studying method for the nuclear matter is the relativistic nuclear many-body theory. Starting from the dynamics of the constituent particle of the system, this theory can be used to discuss the properties of the nuclear matter according to the principle of the statistic thermodynamics. From the relativistic quantum hadrodynamic (QHD) model, some properties of the hot and dense nuclear matter has been studied in this paper under the formalism of finite temperature field theory.For the first part of the thesis, the varization of the effective nucleon mass (M*) as the function of the temperature (T) and the chemical potential (n} is investigated within the QHD-I model in detail, in particular the behavior of M* at high temperature. The multi-value for the selfconsistent equation of the effective nucleon mass has been found in the high temperature region. From this phenomenon we assume that there may be a phase transition in this region. Consequently, we verified the liquid-gas (L-G) phase transition by giving the P - p phase diagram at high temperature. At the same time we conclude that the multi-value for the effective nucleon mass corresponds to the existence of the phase transition of the nuclear system. To verify this conclusion, we take the well-known L-G at the low temperature as an example. It is found that the effective nucleon mass at the region of the phase transition presents the multi-solution. It is worth to note that the new phase at high temperature is still at hadron level since there is no quark in the model we discussed. The phase transition at high temperature is also found in QHD-II model.It is widely accepted that all the thermodynamic phase transition must have the dynamic background. Following the same method which has been used to analyse the phase transition at the mocular level, we investigate the behavor of the nucleon-nucleon intera-tion potential at different temperature and chemical potential through calculating the Debye screening massses of the mesons in the nuclear matter. We found that the temperature and the chemical potential when the potential well disappears accords to the critical ones for the phase transition given by the: P - p diagram. Thus the dynamical background for the phase transition at the nucleon level is provided from the disappearance of the nucleon-nucleon interacting potential well and the disaggregation of the nucleon abound.In recent years, the investigations on the in-mediium fields attract special attentionsbecause they have different behaviors from those in free space. On the one hand, the concepts of the quasi-particle or excitation mode are introduced to describe the medium effect of a hot and dense system, many interesting jobs are performed to study the in-medium properties of the bosons and fermions, such as the dispersion relation, effective mass, damping (decay rate) and width (lifetime), etc.. On the other hand, the medium characters related to the in-medium fields should be reflected by two simple functions, the dielectric function (e) and magnetic permeability (u-1). These two quantities remark the in-medium effect from the point of view of the modified electric field and magnetic field, from which the hot and dense medium effects can also be investigated.The dielectric function and magnetic permeability are are proposed to describe the medium properties in the classical electrodynamics originally and then applied to study the behavior of the Quantum Electrodynamics (QED). There the dielectric function and magnetic permeability are defined by the modifications of the in-medium fields from their vacuum values. It is noted that the field tensor of the QCD can also be decomposed into a electon-like and a magnet-like components as in the QBD theory. The color dielectric function and the color magnetic permeability ajre proposed to describe the color dielectric properties of the QCD medium. In order to discuss the difference for the properties of the in-medium meson and the in-v更多还原