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arXiv 0911.2872gr-qchep-th
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广义洛夫洛克引力

Generalized Lovelock gravity

Qasem Exirifard

摘要:

在黎曼几何中,如果黎曼张量与度规无关,则任意拉格朗日量的度规运动方程可以简洁地表示为作用量关于黎曼张量的第一变分。我们把这种变化称为E张量。注意到E张量和一般Lovelock引力的运动方程具有相同的微分阶,我们定义广义Lovelock引力为从Riemann张量及其任意协变导数构造的多项式标量密度,使得它们导致E张量和度规的运动方程具有相同的微分阶。我们考虑拉格朗日密度函数的度量和第一协变导数的黎曼张量。然后,我们提出了第一个非平凡的例子,广义洛夫洛克引力项。

英文摘要:

In the Riemann geometry, the metric's equation of motion for an arbitrary Lagrangian is succinctly expressed in term of the first variation of the action with respect to the Riemann tensor if the Riemann tensor were independent of the metric. Let this variation be called the E-tensor. Noting that the E-tensor and equations of the motion for a general Lovelock gravity have the same differential degree, we define generalized Lovelock gravity as polynomial scalar densities constructed out from the Riemann tensor and its arbitrary covariant derivatives such that they lead to the same differential degree for the E-tensor and the metric's equation of motion. We consider Lagrangian densities which are functional of the metric and the first covariant derivative of the Riemann tensor. We then present the first non-trivial examples of the generalized Lovelock gravity terms.

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