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arXiv 2012.13709math-phmath.MP
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哈密顿力学向三维相空间的推广

Generalization of Hamiltonian Mechanics to a Three Dimensional Phase Space

Naoki Sato

AI总结:

该研究将经典哈密顿力学推广至三维相空间,用广义泊松括号和辛3-形式替代经典结构,证明了类似李-达布定理的结论,并指出基本恒等式是比辛3-形式闭性更强的条件。

摘要:

经典哈密顿力学通过泊松括号作用于哈密顿函数来实现。哈密顿函数是系统的一个运动常数(即能量)。泊松括号的性质被封装在辛2-形式——一种闭的二阶微分形式——之中。由于闭性,辛2-形式由哈密顿流保持,并且通过李-达布定理在相空间上赋予一个不变(刘维尔)测度。在本文中,我们提出将经典哈密顿力学推广到三维相空间:用作用于一对哈密顿函数的广义泊松括号取代经典泊松括号,同时用辛3-形式取代辛2-形式。我们证明,利用辛3-形式的闭性,存在与经典李-达布定理类似的结论:在局部存在光滑坐标,使得辛3-形式的分量为常数,且相空间被赋予一个守恒体积元。此外,与经典理论一样,广义泊松括号的雅可比恒等式在数学上表达了相关辛形式的闭性。由此,常值反对称三阶逆变张量总能定义广义泊松括号。这与将基本恒等式假设为雅可比恒等式替代物的哈密顿力学推广形成对比。我们特别发现,基本恒等式代表了比辛3-形式闭性更强的要求。

英文摘要:

Classical Hamiltonian mechanics is realized by the action of a Poisson bracket on a Hamiltonian function. The Hamiltonian function is a constant of motion (the energy) of the system. The properties of the Poisson bracket are encapsulated in the symplectic 2-form, a closed second order differential form. Due to closure, the symplectic 2-form is preserved by the Hamiltonian flow, and it assigns an invariant (Liouville) measure on the phase space through the Lie-Darboux theorem. In this paper we propose a generalization of classical Hamiltonian mechanics to a three-dimensional phase space: the classical Poisson bracket is replaced with a generalized Poisson bracket acting on a pair of Hamiltonian functions, while the symplectic 2-form is replaced by a symplectic 3-form. We show that, using the closure of the symplectic 3-form, a result analogous to the classical Lie-Darboux theorem holds: locally, there exist smooth coordinates such that the components of the symplectic 3-form are constants, and the phase space is endowed with a preserved volume element. Furthermore, as in the classical theory, the Jacobi identity for the generalized Poisson bracket mathematically expresses the closure of the associated symplectic form. As a consequence, constant skew-symmetric third order contravariant tensors always define generalized Poisson brackets. This is in contrast with generalizations of Hamiltonian mechanics postulating the fundamental identity as replacement for the Jacobi identity. In particular, we find that the fundamental identity represents a stronger requirement than the closure of the symplectic 3-form.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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