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arXiv · 1510.04573

Nonfreeness and related functionals for measuring correlation in many-fermion states

Alex D. Gottlieb·Norbert J. Mauser
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Abstract

This article is a brief review of "nonfreeness" and related measures of "correlation" for many-fermion systems. The many-fermion states we deem "uncorrelated" are the gauge-invariant quasi-free states. Uncorrelated states of systems of finitely many fermions we call simply "free" states. Slater determinant states are free; all other free states are "substates" of Slater determinant states or limits of such. The nonfreeness of a many-fermion state equals the minimum of its entropy relative to all free states. Correlation functionals closely related to nonfreeness can be defined in terms of R\'enyi entropies; nonfreeness is the one that uses Shannon entropy. These correlation functionals all share desirable additivity and monotonicity properties, but nonfreeness has some additional attractive properties.

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Alex D. Gottlieb, Norbert J. Mauser. 2015-10-15. Nonfreeness and related functionals for measuring correlation in many-fermion states. https://arxiv.org/abs/1510.04573

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