Suppose that we take a bin and gently and uniformly pour in a granular material.As the material in the bin builds up we can identify a surface and ask the question what is the magnitude of the fluctuation in the height of surface? Also of interst is the length scale of the surface fluctuations and how they behave dynamically as more material is added. We assume that particles are deposited uniformly. There is a weak flux i.e. there are no correlations between incoming particles. Particles settle gently so that there is no cooperative reorganization. These assumptions can be considered as part of the definition of the problem.
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机译：假设我们拿一个垃圾箱，轻轻地倒入粒状材料。箱中的材料建立起来，我们可以识别表面并询问表面高度波动的大小是多少？ INT OR INTERST是表面波动的长度，以及它们如何随着更多材料而动态行事。我们假设颗粒均匀地沉积。有一种弱助焊剂I.E.输入粒子之间没有相关性。颗粒轻轻沉降，因此没有合作重组。这些假设可以被视为问题定义的一部分。
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