纯态玻色子浴的热化
Thermalisation by a boson bath in a pure state
摘要：
我们考虑一个与谐振子热浴弱耦合的量子系统。众所周知，这种玻色子浴最初在热平衡时使系统热化。我们表明，假设先验的平衡态是没有必要获得系统的热化。我们确定了完整的薛定谔时间演化的子系统的兴趣的初始纯产品状态的复合系统所考虑的系统和浴。我们发现，该系统松弛到正则平衡，几乎所有的初始纯浴态的宏观定义的能量。系统渐近热态的温度由初始浴态的能量确定为相应的微正则温度。此外，该系统的时间演化与假设玻色子浴最初在该温度下处于热平衡时获得的时间演化相同。我们的方法的一个重要组成部分是适用于其他浴，我们确定的浴功能，这是必要的热化研究。
英文摘要：
We consider a quantum system weakly coupled to a large heat bath of harmonic oscillators. It is well known that such a boson bath initially at thermal equilibrium thermalises the system. We show that assuming a priori an equilibrium state is not necessary to obtain the thermalisation of the system. We determine the complete Schrödinger time evolution of the subsystem of interest for an initial pure product state of the composite system consisting of the considered system and the bath. We find that the system relaxes into canonical equilibrium for almost all initial pure bath states of macroscopically well-defined energy. The temperature of the system asymptotic thermal state is determined by the energy of the initial bath state as the corresponding microcanonical temperature. Moreover, the time evolution of the system is identical to the one obtained assuming that the boson bath is initially at thermal equilibrium with this temperature. A significant part of our approach is applicable to other baths and we identify the bath features which are requisite for the thermalisation studied.
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