In a previous study I defined the nonequilibrium entropy of classical waves in terms of the density matrix of the wave amplitude (the square root of the wave action density). In the present work, I derive the H-theorem for this entropy for weak nonlinear waves whose equations of motion are written in a symplectic form. This formulation enables us to define the Helmholtz free energy of waves in classical plasmas.

中文翻译：

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波熵的H定理

在先前的研究中，我根据波幅的密度矩阵（波作用密度的平方根）定义了经典波的非平衡熵。在目前的工作中，我导出了弱非线性波的熵的H定理，该弱非线性波的运动方程以辛形式表示。该公式使我们能够定义经典等离子体中波的亥姆霍兹自由能。