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arXiv 1402.1944cond-mat.stat-mechcond-mat.quant-gas
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热张量态的量子猝灭:边界效应和广义Gibbs系综

Quantum quench from a thermal tensor state: boundary effects and generalized Gibbs ensemble

Mario Collura, Dragi Karevski

摘要:

我们考虑非相互作用一维费米子场论中的量子猝灭。尺寸为$L$的体系首先制备成两半$\mathcal{L}$($[-L/2,0]$)和$\mathcal{R}$($[0,L/2]$),它们中的每一个分别在两个不同的温度下热化,${T_{L}}$和${T_{R}}$。在给定的时间,两半通过局部耦合连接在一起,整个系统保持酉演化。对于一个无限扩展的系统($L\rightarrow \infty$),我们表明,粒子和能量密度的时间演化是很好地描述通过流体动力学的方法,使我们能够评估相应的固定电流。我们表明,在这种情况下,推导出的两点关联函数,在大的时候,从一个简单的非平衡稳态。否则,每当边界条件被保留(在一个适当定义的热力学极限),任何电流被抑制在大的时间,和稳态描述的广义吉布斯系综,这是对角的,只取决于后淬火模式占领。

英文摘要:

We consider a quantum quench in a non-interacting fermionic one-dimensional field-theory. The system of size $L$ is initially prepared into two halves $\mathcal{L}$ ($[-L/2,0]$) and $\mathcal{R}$ ($[0,L/2]$), each of them thermalized at two different temperatures, ${T_{L}}$ and ${T_{R}}$ respectively. At a given time the two halves are joined together by a local coupling and the whole system is left to evolve unitarily. For an infinitely extended system ($L\rightarrow \infty$), we show that the time evolution of the particle and energy densities is well described via a hydrodynamic approach which allows us to evaluate the correspondent stationary currents. We show, in such a case, that the two-point correlation functions are deduced, at large times, from a simple non-equilibrium steady state. Otherwise, whenever the boundary conditions are retained (in a properly defined thermodynamic limit), any current is suppressed at large times, and the stationary state is described by a generalized Gibbs ensemble, which is diagonal and depends only on the post-quench mode occupation.

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