超越常规微扰理论的自旋玻色子动力学
Spin-boson dynamics beyond conventional perturbation theories
摘要：
提出了一种新的近似方案来描述自旋玻色子问题的动力学。作为非微扰的耦合强度，也不是在隧穿频率，它给出了可靠的结果在很宽的范围内的温度和耦合强度的热环境的一大类浴光谱密度。我们使用路径积分的方法，并从一个广义主方程（GME）的形式的两能级系统的人口差异的精确解。然后，我们近似间的光点和光点逗留的相互作用，以线性顺序，同时保留所有的内部光点的相关性，找到内核进入GME的分析形式。我们的近似方案，我们称之为弱相互作用的光点近似（WIBA），完全同意与传统的微扰近似的隧道矩阵元（非相互作用的光点近似）或在系统浴耦合强度。
英文摘要：
A novel approximation scheme is proposed to describe the dynamics of the spin-boson problem. Being nonperturbative in the coupling strength nor in the tunneling frequency, it gives reliable results over a wide regime of temperatures and coupling strength to the thermal environment for a large class of bath spectral densities. We use a path-integral approach and start from the exact solution for the two-level system population difference in the form of a generalized master equation (GME). Then, we approximate inter-blip and blip-sojourns interactions up to linear order, while retaining all intra-blip correlations to find the kernels entering the GME in analytical form. Our approximation scheme, which we call Weakly-Interacting Blip Approximation (WIBA), fully agrees with conventional perturbative approximations in the tunneling matrix element (Non-Interacting Blip Approximation) or in the system-bath coupling strength.
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