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arXiv 0712.2272math-phmath.MP
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非完整场论的对称性

Symmetry aspects of nonholonomic field theories

J. Vankerschaver, D. Martin de Diego

摘要:

本文讨论对称性存在下非完整场论的发展。前面已经讨论了垂直对称的情况,现在我们讨论对称作用也可以有水平分量的情况。作为这个方向的第一步,我们导出了非完整场论的场方程的一种新的方便形式。非完整对称性,然后介绍了作为对称发电机的虚功为零沿约束子流形,我们表明,对于每一个这样的对称性,存在一个所谓的动量方程,描述的相关组件的动量映射的演变。与基本的几何哲学保持一致,对动量引理的推导作一个小的修改,使我们也能处理广义非完整对称性,即沿投影的向量场。这种对称性出现在非完整场论的实例中,如Cosserat棒,我们恢复了能量守恒(以前已知的结果),以及与空间平移相关的修正的守恒定律。

英文摘要:

The developments in this paper are concerned with nonholonomic field theories in the presence of symmetries. Having previously treated the case of vertical symmetries, we now deal with the case where the symmetry action can also have a horizontal component. As a first step in this direction, we derive a new and convenient form of the field equations of a nonholonomic field theory. Nonholonomic symmetries are then introduced as symmetry generators whose virtual work is zero along the constraint submanifold, and we show that for every such symmetry, there exists a so-called momentum equation, describing the evolution of the associated component of the momentum map. Keeping up with the underlying geometric philosophy, a small modification of the derivation of the momentum lemma allows us to treat also generalized nonholonomic symmetries, which are vector fields along a projection. Such symmetries arise for example in practical examples of nonholonomic field theories such as the Cosserat rod, for which we recover both energy conservation (a previously known result), as well as a modified conservation law associated with spatial translations.

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