"Nonfreeness" is the (negative of the) difference between the von Neumann entropies of a given many-fermion state and the free state that has the same 1-particle statistics. It also equals the relative entropy of the two states in question, i.e., it is the entropy of the given state relative to the corresponding free state. The nonfreeness of a pure state is the same as its "particle-hole symmetric correlation entropy", a variant of an established measure of electron correlation. But nonfreeness is also defined for mixed states, and this allows one to compare the nonfreeness of subsystems to the nonfreeness of the whole. Nonfreeness of a part does not exceed that in the whole; nonfreeness is additive over independent subsystems; and nonfreeness is superadditive over subsystems that are independent on the 1-particle level.
Correlation in fermion or boson systems as the minimum of entropy relative to all free states
在多费米子系统中，“关联”指的是独立粒子模型的不足。使用“自由”状态作为我们的独立粒子模型的原型，我们提出了一个相关性的度量，我们称之为“非自由性”[Int. J. Quant. Inf.5，815（2007）]。多费米子态的非自由度定义为多费米子态相对于具有相同1-矩阵的唯一自由态的熵。本文证明了一个态的非自由度是它的熵相对于所有自由态的最小值。我们还将非自由度的定义扩展到多玻色子态，并讨论了几个例子。
Local classical correlations between physical electrons in Hubbard systems
SISSA, Scuola Internazionale Superiore di Studi Avanzati（国际高等研究院）；CNR–IOM, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche（材料研究所，意大利国家研究委员会）
Arnold Sommerfeld Centre for Theoretical Physics, Ludwig-Maximilians-Universität München（慕尼黑路德维希-马克西米利安大学阿诺德·索末菲理论物理中心）；Department of Computer Science, Oslo Metropolitan University（奥斯陆城市大学计算机系）；Department of Physical Chemistry, University of Geneva（日内瓦大学物理化学系）
Quantization Mapping on Dirac Dynamics via Voltage-Driven Charge Density in Monolayer Graphene: A Klein Paradox and Entropy-Ruled Wavevector Mechanics Study
KPR Institute of Engineering and Technology（KPR工程技术学院）
