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从精确对角化到DMRG:横场伊辛模型的完整数值研究

From Exact Diagonalization to DMRG: A Complete Numerical Study of the Transverse-Field Ising Model

Chandra Sekhar Prayaga

arXiv 2607.28471首次发表:更新:

AI 中文总结

本研究对一维横场伊辛模型开展完整数值研究,采用精确对角化与DMRG方法,解决收敛伪影后提取相变中心电荷,验证其与二维伊辛模型的一致性,兼具物理成果与方法学示例价值。

AI 中文摘要

我们对一维横场伊辛模型(TFIM)开展了自包含的数值研究,追踪其基态纠缠结构,覆盖从小系统尺寸(L=8、14、20)的精确对角化,到最大L=100的密度矩阵重整化群(DMRG)计算。所有7种系统尺寸均采用单一、一致的方法——相同的场网格、相同的收敛判据(每个键维度chi=100和chi=200的独立运行),并明确展示了精确对角化与DMRG必须完全一致而非仅近似一致的情形。研究过程中,我们记录并解决了一种键维度收敛伪影,该伪影曾在早期较不系统的数据集中产生虚假不连续性,可作为从业者的警示示例。利用解决后的数据集,我们通过两种互补途径提取相变的中心电荷:链中间熵的领先对数有限尺寸标度,以及同时应用于所有系统尺寸所有键的完整Calabrese-Cardy公式,在系统排除短程晶格修正后得到c_eff为0.51-0.52,与精确二维伊辛值c=1/2一致。我们回顾了支撑该一致性的量子-经典(Suzuki-Trotter)对应关系,并讨论Widom-Kadanoff标度假设如何从经典问题过渡到量子问题。本手稿既是一项物理研究成果,也是严谨有限尺寸数值计算的方法学示例。

英文摘要

We present a self-contained numerical study of the one-dimensional transverse-field Ising model (TFIM), tracing its ground-state entanglement structure from exact diagonalization at small system size (L=8,14,20) through density-matrix renormalization group (DMRG) calculations up to L=100. A single, consistent methodology - identical field grid, identical convergence diagnostic (independent runs at bond dimensions chi=100 and chi=200 at every point) - is used across all seven system sizes, and we show explicitly where exact diagonalization and DMRG must agree exactly rather than merely approximately. Along the way we document and resolve a bond-dimension convergence artifact that produced a spurious discontinuity in an earlier, less systematic dataset, as a worked cautionary example for practitioners. Using the resolved dataset we extract the central charge of the transition via two complementary routes - the leading logarithmic finite-size scaling of the mid-chain entropy, and the full Calabrese-Cardy formula applied to every bond of every system size simultaneously - obtaining c_eff to 0.51-0.52 as short-distance lattice corrections are systematically excluded, consistent with the exact two-dimensional Ising value c=1/2. We review the quantum-classical (Suzuki-Trotter) correspondence that underlies this agreement and discuss how the Widom-Kadanoff scaling hypothesis transplants from the classical to the quantum problem. The manuscript is intended as both a physics result and a worked methodological example of careful finite-size numerics.

Comments9 pages, 5 figures

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