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arXiv 0912.4258hep-th
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能量和振幅的正性

Energy's and amplitudes' positivity

Alberto Nicolis, Riccardo Rattazzi, Enrico Trincherini

摘要:

在QFT中,经典场组态的零能量条件(NEC)通常与该组态对小扰动的稳定性以及这些扰动的亚亮度有关。在这里,我们展示了一个有效场论,允许稳定的NEC违规的解决方案,正好腔激发。该模型是最近推出的“伽利略”,或更准确地说,其共形不变的版本。我们表明,该理论的低能量S-矩阵服从标准的正性所隐含的色散关系。然而,我们也表明,如果相关的NEC违反的解决方案是在有效的理论,那么其他(通用)的解决方案允许超光速信号传播。虽然我们的例子没有遵循亚亮度和积极性之间的通常联系,但NEC和亚亮度之间的联系是,尽管比通常的方式更不直接。

英文摘要:

In QFT, the null energy condition (NEC) for a classical field configuration is usually associated with that configuration's stability against small perturbations, and with the sub-luminality of these. Here, we exhibit an effective field theory that allows for stable NEC-violating solutions with exactly luminal excitations only. The model is the recently introduced `galileon', or more precisely its conformally invariant version. We show that the theory's low-energy S-matrix obeys standard positivity as implied by dispersion relations. However we also show that if the relevant NEC-violating solution is inside the effective theory, then other (generic) solutions allow for superluminal signal propagation. While the usual association between sub-luminality and positivity is not obeyed by our example, that between NEC and sub-luminality is, albeit in a less direct way than usual.

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