Research on nuclear thermodynamical properties via microscopic theories and applications to nuclear astrophysics

微观理论研究核热力学性质及其在核天体物理中的应用

基本信息

批准号：
15340070
负责人：
NAKADA Hitoshi
金额：
$ 8.7万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

We have studied thermodynamical properties of atomic nuclei and related topics, and have obtained the following results.1. We have developed a convenient technique of angular-momentum projection in the shell model Monte Carlo method, and have applied it to investigate spin-dependence of nuclear level densities. By numerical calculations on Fe-Ni nuclei, we have found that the pair correlation influences low-energy densities of even-even nuclei, which disappears as the energies goes higher, and that such effects are not viewed in odd nuclei.2. We have implemented calculation of level densities of well-deformed nuclei in the rare-earth region, such as ^<162>Dy, and succeeded in reproducing experimental data in wide energy region.3. We have reformulated quantum-number projection in finite-temperature mean-field theories, and moreover, have formulated a BCS-type theory in canonical ensembles for the first time. These have been applied to investigate role of conservation laws in phase transition in finite systems for increasing temperature, the superfluid-to-normal transition in particular. We have pointed out that the S-shape heat capacity of nuclei, which had been suggested to be a fingerprint of the superfluid-to-normal transition, comes out because of the particle-number conservation.4. We have developed a new algorithm for Hartree-Fock-Bogolyubov calculations by applying the Gaussian expansion method, in order to investigate shell structure in unstable nuclei and effects of the pairing correlation. Shell structure around the new magic numbers N=16 and 32 depends on effective interactions. However, the shell gap is almost compensated by the pairing gap in the HFB calculations.

我们对原子核的热力学性质及相关课题进行了研究，得到了以下结果： 1．我们在壳模型蒙特卡罗方法中开发了一种方便的角动量投影技术，并将其应用于研究核能级密度的自旋依赖性。通过对Fe-Ni原子核的数值计算，我们发现偶偶核的对相关性会影响低能量密度，随着能量的升高这种影响会消失，而奇数核则不会出现这种影响。 2．实现了^<162>Dy等稀土区良好变形核能级密度的计算，并成功再现了宽能区的实验数据。 3．我们重新表述了有限温度平均场理论中的量子数投影，并且首次在正则系综中表述了BCS型理论。这些已应用于研究守恒定律在有限系统中温度升高的相变中的作用，特别是超流体到正常的转变。我们指出，由于粒子数守恒，原子核的S形热容被认为是超流体到正常转变的指纹。4．我们应用高斯展开法开发了一种新的 Hartree-Fock-Bogolyubov 计算算法，以研究不稳定核中的壳结构和配对相关性的影响。新幻数 N=16 和 32 周围的壳结构取决于有效的相互作用。然而，壳间隙几乎被 HFB 计算中的配对间隙补偿。