粘性问题：粘性/熵密度约束的现状
A sticky business: the status of the conjectured viscosity/entropy density bound
摘要：
关于剪切粘度η与熵密度s之比η/s存在一个普遍的下界的猜想有许多种形式，有几种不同的有效性域。我们检查各种形式的猜想。我们认为，一些变种的猜想是不可行的，由于存在理论上一致的反例。我们还注意到，许多支持界限的证据并不适用于尚未被排除的变体。
英文摘要：
There have been a number of forms of a conjecture that there is a universal lower bound on the ratio, eta/s, of the shear viscosity, eta, to entropy density, s, with several different domains of validity. We examine the various forms of the conjecture. We argue that a number of variants of the conjecture are not viable due to the existence of theoretically consistent counterexamples. We also note that much of the evidence in favor of a bound does not apply to the variants which have not yet been ruled out.
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