arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 0910.4979nucl-th
收藏

自旋不饱和核的改进密度矩阵展开

An improved density matrix expansion for spin-unsaturated nuclei

B. Gebremariam, T. Duguet, S. K. Bogner

摘要:

低能核理论的一个当前目标是从核子间相互作用和多体微扰理论(MBPT)建立非经验核能密度泛函(EDF)。Negele和Vautherin的密度矩阵展开(DME)是将高度非局域的Hartree-Fock表达式映射成具有密度依赖耦合的准局域Skyrme泛函的一种简便方法。在这项工作中,我们评估的准确性的DME在再现的非本地交换(福克)的能源贡献。在对比的标量部分的密度矩阵的Negele和Vautherin的原始配方是相当准确的,我们证明的必要性,重新制定DME的矢量部分的密度矩阵,这是需要一个准确的描述自旋不饱和核。相空间平均技术示出产生显着改善的密度矩阵的矢量部分相比,Negele和Vautherin的原始配方。提高精度的关键是要考虑到各向异性的特点,在有限费米系统的表面区域的局部动量分布。分别优化DME的中心,张量和自旋轨道贡献的福克能量,一个达到百分之几的准确性超过一组代表性的半幻核。有了这样的精度在手,人们可以设想使用相应的Skyrme能量泛函作为一个微观约束的起点,未来的唯象参数化可以建立和完善。

英文摘要:

A current objective of low-energy nuclear theory is to build non-empirical nuclear energy density functionals (EDFs) from underlying inter-nucleon interactions and many-body perturbation theory (MBPT). The density matrix expansion (DME) of Negele and Vautherin is a convenient method to map highly non-local Hartree-Fock expressions into the form of a quasi-local Skyrme functional with density-dependent couplings. In this work, we assess the accuracy of the DME at reproducing the non-local exchange (Fock) contribution to the energy. In contrast to the scalar part of the density matrix for which the original formulation of Negele and Vautherin is reasonably accurate, we demonstrate the necessity to reformulate the DME for the vector part of the density matrix, which is needed for an accurate description of spin-unsaturated nuclei. Phase-space averaging techniques are shown to yield a significant improvement for the vector part of the density matrix compared to the original formulation of Negele and Vautherin. The key to the improved accuracy is to take into account the anisotropy that characterizes the local-momentum distribution in the surface region of finite Fermi systems. Optimizing separately the DME for the central, tensor and spin-orbit contributions to the Fock energy, one reaches a few-percent accuracy over a representative set of semi-magic nuclei. With such an accuracy at hand, one can envision using the corresponding Skyrme-like energy functional as a microscopically-constrained starting point around which future phenomenological parameterizations can be built and refined.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑