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arXiv 1202.2681nucl-thcond-mat.supr-connucl-ex
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粒子输运中的配对动力学

Pairing dynamics in particle transport

G. Scamps, D. Lacroix, G. F. Bertsch, K. Washiyama

摘要:

我们分析了基于Hartree-Fock-Bogoliubov(HFB)或BCS近似的含时理论中配对对粒子输运的影响。HFB密度矩阵的运动方程是唯一的,并且该理论遵守由守恒量与哈密顿量的交换子定义的通常守恒律。相比之下,基于BCS近似的理论更有问题。在通常的TDHF+BCS公式中,连续性连续性方程被违反,人们看到粒子密度的非物理振荡。这可以通过在TDHF+BCS的演化过程中冻结占据数来改善,但BCS存在其他问题,使其对反应动力学产生怀疑。我们还比较了不同的数值实现的时间相关的HFB方程。$U$和$V$ Bogoliubov变换的运动方程不是唯一的,但通常的公式似乎也是最有效的。最后,我们比较了含时的HFB解与两粒子薛定谔方程的数值精确解。取决于初始状态的处理,HFB动力学在短时间内产生类似于薛定谔方程的粒子发射率。在很长一段时间内,由于HFB理论固有的平均场近似,总的粒子发射可能会有很大的不同。

英文摘要:

We analyze the effect of pairing on particle transport in time-dependent theories based on the Hartree-Fock-Bogoliubov (HFB) or BCS approximations. The equations of motion for the HFB density matrices are unique and the theory respects the usual conservation laws defined by commutators of the conserved quantity with the Hamiltonian. In contrast, the theories based on the BCS approximation are more problematic. In the usual formulation of TDHF+BCS, the equation of continuity is violated and one sees unphysical oscillations in particle densities. This can be ameliorated by freezing the occupation numbers during the evolution in TDHF+BCS, but there are other problems with the BCS that make it doubtful for reaction dynamics. We also compare different numerical implementations of the time-dependent HFB equations. The equations of motion for the $U$ and $V$ Bogoliubov transformations are not unique, but it appears that the usual formulation is also the most efficient. Finally, we compare the time-dependent HFB solutions with numerically exact solutions of the two-particle Schrodinger equation. Depending on the treatment of the initial state, the HFB dynamics produces a particle emission rate at short times similar to that of the Schrodinger equation. At long times, the total particle emission can be quite different, due to inherent mean-field approximation of the HFB theory.

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