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arXiv 1601.07129cond-mat.stat-mech
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温度不是超统计学中的观测量

Temperature is not an observable in superstatistics

Sergio Davis, Gonzalo Gutiérrez

摘要:

超统计学(英语:Superstatistics)(Physica A 322,267-275,2003)是一种形式主义,它试图解释自然界中玻尔兹曼-吉布斯分布以外的分布的存在,通常是幂律行为,对于不平衡的系统,如湍流下的流体,等离子体和引力系统。超统计学假设这些系统是在不同温度下的正则系综的叠加中发现的。通常的解释是局部热平衡(LTE),即在不同的空间区域或时刻的不均匀温度分布。在这里,我们表明,为了使超统计量是内部一致的,它是不可能定义一个相空间函数或可观察$B(p, q)$对应的局部值的$β=1/k_B T$一对一。温度则属于与能量不同的一类可观测量,能量具有作为相空间函数的哈密顿量$\mathcal{H}(p, q)$。我们证明的一个重要结果是,在超统计中,温度与动能的识别仅限于$β$的期望,不能用于测量LTE中的不同温度或其波动。

英文摘要:

Superstatistics (Physica A 322, 267-275, 2003) is a formalism that attempts to explain the presence of distributions other than the Boltzmann-Gibbs distributions in Nature, typically power-law behavior, for systems out of equilibrium such as fluids under turbulence, plasmas and gravitational systems. Superstatistics postulates that those systems are found in a superposition of canonical ensembles at different temperatures. The usual interpretation is one of local thermal equilibrium (LTE) in the sense of an inhomogeneous temperature distribution in different regions of space or instants of time. Here we show that, in order for superstatistics to be internally consistent, it is impossible to define a phase-space function or observable $B(p, q)$ corresponding one-to-one to the local value of $β=1/k_B T$. Temperature then belongs to a different class of observables than the energy, which has as a phase-space function the Hamiltonian $\mathcal{H}(p, q)$. An important consequence of our proof is that, in Superstatistics, the identification of temperature with the kinetic energy is limited to the expectation of $β$ and cannot be used to measure the different temperatures in LTE or its fluctuations.

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