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arXiv math-ph/0507008math-phcond-mat.stat-mechhep-thmath.MP
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谱间隙与相关系数的指数衰减

Spectral Gap and Exponential Decay of Correlations

Matthew B. Hastings, Tohru Koma

摘要:

本文研究了一类具有短程相互作用的量子自旋和费米子系统中基态上的能隙与基态关联衰减之间的关系。我们证明了,如果两个可观测量在大的距离彼此反对易,那么非零谱隙意味着相应的相关指数衰减。当两个观测量在远距离上对易时,在间隙假设下,关联关联函数呈指数衰减。如果观测量在系统的整体对称性的U(1)旋转下表现为一个向量,我们使用先前关于关联函数的大距离衰减的结果来证明更强的陈述,即在具有一定自相似性的(分形)维数D<2的晶格上,在间隙假设下,关联函数本身而不仅仅是连接的关联函数是指数衰减的。特别是,如果系统在一个空间方向上是不变性的,那么这个自相似性条件自动满足。我们也治疗系统的长程,幂律衰减相互作用。

英文摘要:

We study the relation between the spectral gap above the ground state and the decay of the correlations in the ground state in quantum spin and fermion systems with short-range interactions on a wide class of lattices. We prove that, if two observables anticommute with each other at large distance, then the nonvanishing spectral gap implies exponential decay of the corresponding correlation. When two observables commute with each other at large distance, the connected correlation function decays exponentially under the gap assumption. If the observables behave as a vector under the U(1) rotation of a global symmetry of the system, we use previous results on the large distance decay of the correlation function to show the stronger statement that the correlation function itself, rather than just the connected correlation function, decays exponentially under the gap assumption on a lattice with a certain self-similarity in (fractal) dimensions D<2. In particular, if the system is translationally invariant in one of the spatial directions, then this self-similarity condition is automatically satisfied. We also treat systems with long-range, power-law decaying interactions.

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