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arXiv 0904.2729cond-mat.stat-mech
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长程相互作用系统的动力学和热力学:不同泛函的解释

Dynamics and thermodynamics of systems with long-range interactions: interpretation of the different functionals

Pierre-Henri Chavanis

摘要:

我们讨论了具有弱长程相互作用的系统的动力学和热力学。一般来说,这些系统经历了一个暴力的碰撞无弛豫的弗拉索夫制度导致(通常)非玻尔兹曼准定态(QSS),其次是缓慢的碰撞弛豫导致玻尔兹曼统计平衡态。这两种状态可以用动力学理论来解释,使用BBGKY等级的1/N幂的扩展,其中N是粒子的数量。我们讨论分析中出现的不同泛函的物理意义:玻尔兹曼熵,林登-贝尔熵,在粗粒度分布函数的约化空间中产生的“广义”熵,Tsallis熵,广义H函数在强弛豫过程中增加(不一定单调)和凸Casimir泛函用于解决形式的非线性动力学稳定性的Vlasov方程的稳态。我们展示了与这些泛函相关的不同变分问题之间的联系。我们还介绍了一般类的非线性平均场Fokker-Planck(NFP)方程,可用作数值算法来解决这些约束优化问题。

英文摘要:

We discuss the dynamics and thermodynamics of systems with weak long-range interactions. Generically, these systems experience a violent collisionless relaxation in the Vlasov regime leading to a (usually) non-Boltzmannian quasi stationary state (QSS), followed by a slow collisional relaxation leading to the Boltzmann statistical equilibrium state. These two regimes can be explained by a kinetic theory, using an expansion of the BBGKY hierarchy in powers of 1/N, where N is the number of particles. We discuss the physical meaning of the different functionals appearing in the analysis: the Boltzmann entropy, the Lynden-Bell entropy, the "generalized" entropies arising in the reduced space of coarse-grained distribution functions, the Tsallis entropy, the generalized H-functions increasing during violent relaxation (not necessarily monotonically) and the convex Casimir functionals used to settle the formal nonlinear dynamical stability of steady states of the Vlasov equation. We show the connection between the different variational problems associated with these functionals. We also introduce a general class of nonlinear mean field Fokker-Planck (NFP) equations that can be used as numerical algorithms to solve these constrained optimization problems.

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