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arXiv 1402.6858math-phcond-mat.stat-mechmath.MPquant-ph
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量子伊辛模型在高斯和多高斯近似下的谱密度

Spectral density of the quantum Ising model in two fields: Gaussian and multi-Gaussian approximations

Y. Y. Atas, E. Bogomolny

摘要:

详细讨论了自旋数$N$较大但有限的量子伊辛模型在两个场中的谱密度。当所有的耦合常数是相同的顺序,在散装的光谱密度很好地近似为一个高斯函数,这是典型的行为与短程相互作用的多体模型。本文的主要部分是专门调查的一个不同的特征情况下,谱密度有峰与强简并的未微扰态在一定限度的耦合常数。在严格的极限$N\to\infty$中,峰重叠并消失,但对于数值计算中可获得的$N$值,它们通常也强烈地影响谱密度和其他量。本文提出了一种简单的方法,它可以找到与数值计算相一致的谱密度多峰结构的一般近似公式。

英文摘要:

Spectral density of quantum Ising model in two fields for large but finite number of spins $N$, is discussed in detail. When all coupling constants are of the same order, spectral densities in the bulk are well approximated by a Gaussian function which is typical behaviour for many-body models with short-range interactions. The main part of the paper is devoted to the investigation of a different characteristic case when spectral densities have peaks related with strong degeneracies of unperturbed states in certain limits of coupling constants. In the strict limit $N\to\infty$, peaks overlap and disappear but for values of $N$ accessible in numerical calculations they often strongly influence spectral densities and other quantities as well. A simple method is developed which permits to find general approximation formulae for multi-peak structure of spectral density in good agreement with numerics.

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。

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