σ介子的自相互作用对核物质物态方程的影响

在相对论σ－ω模型里，详细讨论了σ介子的自相互作用参数对正常核物质物态方程的影响，特别是对核物质的不可压缩系数、有效质量，以及σ介子与核子、ω介子与核子之间的耦合常数的影响，发现这些参数与核物质的性质之间有紧密的联系．同时，利用这些结果研究了相对论σ－ω－π模型下△共振态核物质的结合能和压强与温度之间的关系，并同我们以前的结果作了比较，得到了一些有意义的结果．在以上所有的分析中，考虑了核子、△粒子和σ介子的真空起伏．

手征σ模型中σ介子的质量与核物质结合能曲线关系的研究

文中研究了手征σ模型下σ介子的质量m_σ与核物质结合能曲线的关系,主要的目的是研究在单圈图近似下所谓的“快子极点”问题,即σ或π介子质量的平方变为负数,这将导致能量密度为虚数。把m_σ看成自由参数并通过拟合核物质的饱和性质而确定,结果表明,在单圈图真空起伏近似下,并选重整化点在质量壳上,当m_σ=307.5MeV而且核密度小于4.43倍正常饱和密度时,“快子极点”没有出现,因此首先得到了核物质结合能曲线以及计算了不可压缩系数K(≌175.7MeV)。

σ，ω色散关系中的ρ°－ω混合效应

用标准σ－ω混合方法所构造的介子介电函数，计算了核物质中σ，ω介子的集体激发能谱（或色散关系），并考虑ρ°－ω混合的效应，结果表明ρ°－ω混合对色散关系的影响很小。

Tachyon Pole in σ Meson Propagator in Nuclear Matter in the Relativistic σ—ω Model

The conditions that the tachyon pole of the σ meson propagator in nuclear matter appears are studied in the one-loop approximation in the relativistic σ-ω model. Different from the results of the previous paper, we find that the effect of the constant a in the self-interaction, U(σ) = aσ+ bσ + cσ + dσ , of the σ meson cannot be neglected.It determines the critical density where tachyon appears. The smaller the a, the larger the critical density. The binding energy, pressure, incompressibility coefficient, nucleon effective mass are calculated and the relation between parameters to the tachyon pole is also studied.

Sigma Terms and Strangeness Contents of Baryon Octet in Modified Chiral Perturbation Theory

In the frame work of chiral perturbation theory, a modified effective Lagrangian for meson-baryon system is constructed, where the SU（3） breaking effect for meson is considered. The difference between physical and chiral limlt decay constants is taken into account. Calculated to one 1ooi） at O（p^3）, the sigma terms and strangeness contents of baryon octet are obtained.