Lucas Andrew
Department of Physics, Stanford University, Stanford California 94305, USA.
Phys Rev Lett. 2019 May 31;122(21):216601. doi: 10.1103/PhysRevLett.122.216601.
It has long been believed that dissipative timescales τ obey a "Planckian" bound τ≳(ℏ/k_{B}T) in strongly coupled quantum systems. Despite much circumstantial evidence, however, there is no known τ for which this bound is universal. Here we define operator size at a finite temperature, and conjecture such a τ: the timescale over which small operators become large. All known many-body theories are consistent with this conjecture. This proposed bound explains why previously conjectured Planckian bounds do not always apply to weakly coupled theories, and how Planckian timescales can be relevant to both transport and chaos.
长期以来，人们一直认为，在强耦合量子系统中，耗散时间尺度τ遵循“普朗克”界限τ≳(ℏ/k_{B}T)。然而，尽管有很多间接证据，但尚无已知的τ能使该界限具有普遍性。在这里，我们定义了有限温度下的算符大小，并推测了这样一个τ：小算符变大的时间尺度。所有已知的多体理论都与这一推测一致。这一提出的界限解释了为什么先前推测的普朗克界限并不总是适用于弱耦合理论，以及普朗克时间尺度如何与输运和混沌都相关。
