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arXiv 1206.4449math-phmath.MPphysics.class-ph
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哈密顿点动力学领域的广义诺特定理

Generalized Noether theorem in the realm of Hamiltonian point dynamics

Frankfurt Institute for Advanced Studies(法兰克福高等研究所)

Jürgen Struckmeier

AI总结:

本文研究哈密顿点动力学领域的广义诺特定理,采用扩展哈密顿形式体系推导含时间变换的对称映射,以开普勒系统Runge-Lenz不变量为例验证了该定理的应用。

摘要:

点动力学领域的诺特定理建立了哈密顿-拉格朗日系统的运动常数与其作用量泛函的特定对称变换之间的关联。尽管该定理通常在拉格朗日形式体系中推导,哈密顿形式体系为这种关联提供了自然的语境:正则变换可使作用量的正则形式保持不变,仅差一个边界项;在本文考虑的范畴内,对称变换还会保持指定的扩展哈密顿量的函数形式。当允许依赖动量的变换和边界项时,每个光滑相空间一阶积分在局部都存在对应的正则诺特对称。为了表示包含时间变换的对称映射,本文采用扩展哈密顿形式体系,该体系可定义正则变换的生成函数,除了常规的正则空间与动量变量映射外,还能映射时间和能量;物理能量超曲面与演化参数的选择,需与整个扩展相空间上的恒等式区分开。作为示例,本文推导了与开普勒系统的Runge-Lenz不变量相关的对称变换的显式表示,合适的演化参数选择可使其时间平移代表成为指定扩展作用量的对称。

英文摘要:

Noether's theorem in the realm of point dynamics establishes the correlation of a constant of motion of a Hamilton-Lagrange system with a particular symmetry transformation of its action functional. Although usually derived in the Lagrangian formalism, the Hamiltonian formalism provides a natural context for this correlation. Canonical transformations preserve the canonical form of the action up to a boundary term. Within the class considered here, a symmetry additionally preserves the functional form of the specified extended Hamiltonian. Every smooth phase-space first integral admits locally a corresponding canonical Noether symmetry when momentum-dependent transformations and boundary terms are allowed. In order to represent symmetry mappings that include a transformation of time, we use the extended Hamiltonian formalism. This formalism enables us to define generating functions of canonical transformations that also map time and energy in addition to the conventional mappings of canonical space and momentum variables. The physical energy hypersurface and the choice of the evolution parameter are distinguished from identities on the full extended phase space. As an example, a manifest representation of the symmetry transformation associated with the Runge-Lenz invariant of the Kepler system is derived. A suitable choice of evolution parameter makes its time-shifting representative a symmetry of the specified extended action.

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