有限温度晶格中能量扩散的研究方法
Methods of exploring energy diffusion in lattices with finite temperature
摘要：
本文讨论了有限温度晶格中能量扩散的两种研究方法。第一种是能量反冲（EK）方法。为了应用这种方法，人们将外部能量踢加到晶格中的粒子上，并通过演化被踢系统来跟踪其演化。第二种方法是波动相关法。对正则系综计算概率密度函数的公式作了一些修正，并推广到微正则系综。我们表明FC方法在理论和技术上都优于EK方法。从理论上讲，FC方法得到的PDF反映了内能的扩散过程，而EK方法得到的PDF反映了反冲能的扩散过程。系统的内能和外加能的扩散过程，即，反冲能量可以根据模型而在数量上甚至在质量上不同。为了说明这些事实，我们不仅研究了平衡系统，而且研究了定态非平衡系统。实例表明，在这两种情况下的内能和踢能可能有不同的扩散行为的报告。技术上的优势使我们能够研究长时间的扩散过程，从而避免了有限时间效应。
英文摘要：
We discuss two methods for exploring energy diffusion in lattices with finite temperature in this paper. The first one is the energy-kick (EK) method. To apply this method, one adds an external energy kick to a particle in the lattice, and tracks its evolution by evolving the kicked system. The second one is the fluctuation-correlation (FC) method. The formula for calculating the probability density function (PDF) using the canonical ensemble is slightly revised and extended to the microcanonical ensemble. We show that the FC method has advantages over the EK method theoretically and technically. Theoretically, the PDF obtained by the FC method reveals the diffusion processes of the inner energy while the PDF obtained by the EK method represents that of the kick energy. The diffusion processes of the inner energy and the external energy added to the system, i.e., the kick energy, may be different quantitatively and even qualitatively depending on models. To show these facts, we study not only the equilibrium systems but also the stationary nonequilibrium systems. Examples showing that the inner energy and the kick energy may have different diffusion behavior are reported in both cases. The technical advantage enables us to study the long-time diffusion processes and thus avoids the finite-time effect.
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