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arXiv 1407.7167cond-mat.str-el
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量子KAM定理的闪光:一维玻色气体中量子猝灭的启示

Glimmers of a Quantum KAM Theorem: Insights from Quantum Quenches in One Dimensional Bose Gases

G. P. Brandino, J. -S. Caux, R. M. Konik

摘要:

量子多体系统中的实时动力学本质上是复杂的,因此难以预测。然而,有一组特殊的系统,这些动力学在理论上是容易处理的:可积模型。这些模型拥有超越能量和动量的非平凡守恒量。这些量被认为控制低维原子气体以及量子自旋链中的动力学和热化。但是,当导致额外守恒量存在的特殊对称性被打破时,会发生什么呢?如果断裂很弱,是否有任何数量的记忆?在这里,在弱可积性破缺的存在下,我们证明了有可能构造剩余准守恒量,从而为KAM定理及其伴随的Nekhoreshev估计提供了量子模拟。我们证明了这种结构明确的背景下,在一维玻色气体的量子猝灭,并认为这些准守恒量可以探测实验。

英文摘要:

Real-time dynamics in a quantum many-body system are inherently complicated and hence difficult to predict. There are, however, a special set of systems where these dynamics are theoretically tractable: integrable models. Such models possess non-trivial conserved quantities beyond energy and momentum. These quantities are believed to control dynamics and thermalization in low dimensional atomic gases as well as in quantum spin chains. But what happens when the special symmetries leading to the existence of the extra conserved quantities are broken? Is there any memory of the quantities if the breaking is weak? Here, in the presence of weak integrability breaking, we show that it is possible to construct residual quasi-conserved quantities, so providing a quantum analog to the KAM theorem and its attendant Nekhoreshev estimates. We demonstrate this construction explicitly in the context of quantum quenches in one-dimensional Bose gases and argue that these quasi-conserved quantities can be probed experimentally.

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