Unphysical and physical solutions in many-body theories: from weak to strong correlation
Unphysical and physical solutions in many-body theories: from weak to strong correlation
复制标题
多体理论中的非物理和物理解：从弱相关到强相关
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
J. Berger
中科院分区：
文献类型：
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作者：
A. Stan;A. Stan;A. Stan;P. Romaniello;S. Rigamonti;L. Reining;J. Berger
多体理论在很大程度上基于自洽方程，这些方程是根据感兴趣的物理量本身（例如密度）构建的。因此，计算重要的性质，如总能量或光电发射光谱，需要解决非线性方程，有非物理和物理的解决方案。在这项工作中，我们将展示在何种情况下，一个运行到一个非物理的解决方案，我们指出如何可以克服这个问题。此外，我们解决了这个难题的时候，以及为什么相互作用的绿色的功能不明确地确定潜在的系统，根据其潜力，或非相互作用的绿色的功能。我们的结果是一般的，因为它们源于方程的基本结构。氟化锂的吸收光谱作为一个例子，我们的方法解释了一些广泛使用的模型的文献中的观察。我们的研究结果适用于弱相关和强相关的制度。对于强相关制度，我们表明，不能使用的表达式，从标准的微扰理论，我们提出了一种不同的方法，是准确的强相互作用的限制。
Many-body theory is largely based on self-consistent equations that are constructed in terms of the physical quantity of interest itself, for example the density. Therefore, the calculation of important properties such as total energies or photoemission spectra requires the solution of nonlinear equations that have unphysical and physical solutions. In this work we show in which circumstances one runs into an unphysical solution, and we indicate how one can overcome this problem. Moreover, we solve the puzzle of when and why the interacting Green’s function does not unambiguously determine the underlying system, given in terms of its potential, or non-interacting Green’s function. Our results are general since they originate from the fundamental structure of the equations. The absorption spectrum of lithium fluoride is shown as one illustration, and observations in the literature for some widely used models are explained by our approach. Our findings apply to both the weak and strong-correlation regimes. For the strong-correlation regime we show that one cannot use the expressions that are obtained from standard perturbation theory, and we suggest a different approach that is exact in the limit of strong interaction.