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arXiv 1708.09620gr-qchep-thmath-phmath.MP
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Killing向量背景下场和膜的Noether对称性

Noether symmetries for fields and branes in backgrounds with Killing vectors

Josep M. Pons

摘要:

我们表明,Belinfante建设一个改进的能量动量张量可以结转到弯曲的背景下,在类比的情况下,平坦的时空。无论背景是动态的还是固定的,非反作用的,结果都成立。事实证明,类似的准正则能量-动量张量一般不是协变守恒的,但它的贝林凡特“改进”是。我们将这最后一个张量与希尔伯特张量通过函数推导拉格朗日量的度量。在非动力学背景下,讨论了与其Killing对称性有关的Noether守恒流以及Belinfante张量所起的作用。接下来,我们研究扩展对象($p$ -膜)无论是在一个动态的或在一个固定的背景下,并获得与目标时空和世界体积超同态的Noether恒等式。我们表明,在场论以及与扩展对象,杀死对称性的背景成为普通的刚性诺特对称性的理论在这个固定的背景。以闵可夫斯基时空中的麦克斯韦理论为例,我们在附录中展示了贝林凡特张量在这些对称性的构造中所起的作用。

英文摘要:

We show that Belinfante construction of an improved energy-momentum tensor can be carried over to curved backgrounds, in analogy to the case of flat spacetime. The results hold irrespective of the background being dynamical or a fixed, non-backreacting one. It turns out that the analogous would-be canonical energy-momentum tensor is not covariantly conserved in general, but its Belinfante "improvement" is. We relate this last tensor with the Hilbert tensor obtained by functionally derivating the Lagrangian with respect to the metric. When the background in non-dynamical, we discuss some issues concerning the Noether conserved currents associated with its Killing symmetries and the role played by the Belinfante tensor. Next we study extended objects ($p$-branes) either in a dynamic or in a fixed background, and obtain the Noether identities associated both with target spacetime and world volume diffeomorphisms. We show that in field theory as well as with extended objects, the Killing symmetries of the background become ordinary rigid Noether symmetries of the theory in this fixed background. With the example of Maxwell theory in Minkowski spacetime we show in an appendix the role of the Belinfante tensor in the construction of these symmetries.

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