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arXiv 1607.01068cond-mat.stat-mechhep-th
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伊辛场论中猝灭的哈密顿截断方法

Hamiltonian truncation approach to quenches in the Ising field theory

Tibor Rakovszky, Márton Mestyán, Mario Collura, Márton Kormos, Gábor Takács

摘要:

在晶格系统中,强大的数值技术,如矩阵产品状态为基础的方法可用于研究非平衡动力学,连续系统的非平衡行为是很难模拟。通过使用截断自由费米子空间方法研究1+1维伊辛场论的量子猝灭动力学,我们在这里证明了汉密尔顿截断方法可以有效地应用于这个问题。在自由马约拉纳费米子场论中,通过对可积猝灭的方法进行基准测试,研究了纵向磁场对可积猝灭扰动的影响.在这两个模型的铁磁和顺磁相,我们发现持续振荡的频率设置的低洼粒子激发不仅小,但即使是中等大小的淬火。在铁磁相,这些粒子是各种非微扰约束束缚态的畴壁激发,而在顺磁相的单磁振子激发支配的动态,使我们能够捕获的磁化强度的时间演变使用的组合的已知结果从微扰理论和形状因子为基础的方法。我们指出,低洼激发的优势,允许通过研究的淬火动力学的质谱的数值或实验测定。

英文摘要:

In contrast to lattice systems where powerful numerical techniques such as matrix product state based methods are available to study the non-equilibrium dynamics, the non-equilibrium behaviour of continuum systems is much harder to simulate. We demonstrate here that Hamiltonian truncation methods can be efficiently applied to this problem, by studying the quantum quench dynamics of the 1+1 dimensional Ising field theory using a truncated free fermionic space approach. After benchmarking the method with integrable quenches corresponding to changing the mass in a free Majorana fermion field theory, we study the effect of an integrability breaking perturbation by the longitudinal magnetic field. In both the ferromagnetic and paramagnetic phases of the model we find persistent oscillations with frequencies set by the low-lying particle excitations not only for small, but even for moderate size quenches. In the ferromagnetic phase these particles are the various non-perturbative confined bound states of the domain wall excitations, while in the paramagnetic phase the single magnon excitation governs the dynamics, allowing us to capture the time evolution of the magnetisation using a combination of known results from perturbation theory and form factor based methods. We point out that the dominance of low lying excitations allows for the numerical or experimental determination of the mass spectra through the study of the quench dynamics.

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