论文标题
静态核中重核的状态密度加上随机相近似
State densities of heavy nuclei in the static-path plus random-phase approximation
论文作者
论文摘要
核状态密度是复合核反应的统计模型的重要输入。状态密度通常是通过不包含重要相关性的自洽的平均场近似值来计算的，并且必须通过经验的集体增强因子来增强。在这里，我们将静态路径加上随机相近似（SPA+RPA）基于SAAMARIUM同位素链中的状态密度，$^{148-155} $ SM SM SM SM SM SM sm Shell shell Model Monte Carlo（SMMMC）方法获得的精确结果（达到统计错误）。 SPA+RPA方法结合了平均场之外的所有静态波动，以及每个静态波动周围的小振幅量化量波动。使用配对加四极相互作用，我们表明SPA+RPA状态密度与偶数和奇数质量同位素的精确SMMC密度非常吻合。对于偶数质量同位素，我们还将结果与有限温度的Hartree-fock-bogoliubov（HFB）近似计算的平均场状态密度进行比较。我们发现，SPA+RPA修复了与变形核中旋转损坏的旋转对称性相关的平均场近似值的缺陷，并违反了配对冷凝物中的粒子量保护。特别是，在变形的核中，SPA+RPA相对于平均场状态密度再现状态密度的旋转增强。
Nuclear state densities are important inputs to statistical models of compound-nucleus reactions. State densities are often calculated with self-consistent mean-field approximations that do not include important correlations and have to be augmented with empirical collective enhancement factors. Here, we benchmark the static-path plus random-phase approximation (SPA+RPA) to the state density in a chain of samarium isotopes $^{148-155}$Sm against exact results (up to statistical errors) obtained with the shell model Monte Carlo (SMMC) method. The SPA+RPA method incorporates all static fluctuations beyond the mean field together with small-amplitude quantal fluctuations around each static fluctuation. Using a pairing plus quadrupole interaction, we show that the SPA+RPA state densities agree well with the exact SMMC densities for both the even- and odd-mass isotopes. For the even-mass isotopes, we also compare our results with mean-field state densities calculated with the finite-temperature Hartree-Fock-Bogoliubov (HFB) approximation. We find that the SPA+RPA repairs the deficiencies of the mean-field approximation associated with broken rotational symmetry in deformed nuclei and the violation of particle-number conservation in the pairing condensate. In particular, in deformed nuclei the SPA+RPA reproduces the rotational enhancement of the state density relative to the mean-field state density.
