Finite-size corrections versus relaxation after a sudden quench
Finite-size corrections versus relaxation after a sudden quench
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有限尺寸修正与突然淬火后的松弛
DOI：
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发表时间：
2012
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通讯作者：
M. Fagotti
中科院分区：
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作者：
M. Fagotti
我们考虑平移不变哈密顿量中全局参数突然淬灭后的时间演化，并研究有限链中的时间平均期望值和纠缠熵。我们证明，在非相互作用模型中，自旋相关函数的时间平均值渐近等于无限链中的无限时间极限，已知这是由广义吉布斯系综描述的。考虑到非局部算子，等价性被打破，我们确定这可以追溯到哈密顿量在淬灭之前和之后共同的守恒定律的存在。我们开发了一种方法来计算时间平均相关函数和纠缠熵的领先有限尺寸校正。我们发现大的修正通常与具有慢弛豫动力学的可观测量相关。
We consider the time evolution after sudden quenches of global parameters in translational invariant Hamiltonians and study the time average expectation values and entanglement entropies in finite chains. We show that in noninteracting models the time average of spin correlation functions is asymptotically equal to the infinite time limit in the infinite chain, which is known to be described by a generalized Gibbs ensemble. The equivalence breaks down considering nonlocal operators, and we establish that this can be traced back to the existence of conservation laws common to the Hamiltonian before and after the quench. We develop a method to compute the leading finite-size correction for time average correlation functions and entanglement entropies. We find that large corrections are generally associated to observables with slow relaxation dynamics.