Pathological behaviour of the scalar graviton in Hořava-Lifshitz gravity
Pathological behaviour of the scalar graviton in Hořava-Lifshitz gravity
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DOI：
10.1007/jhep03(2010)061
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发表时间：
2009-10
影响因子：
5.4
通讯作者：
K. Koyama;F. Arroja
中科院分区：
文献类型：
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作者：
K. Koyama;F. Arroja
我们证实了最近的说法，在红外限制的Hoenava-Lifshitz引力，标量引力子成为鬼，如果声速平方是积极的单位德西特和闵可夫斯基背景。为了避免重影和驯服不稳定性，声速平方应该是负的并且非常小，这意味着流动参数λ应该非常接近其广义相对论（GR）值。我们计算了标量引力子的立方相互作用，结果表明它们与k-暴胀模型中的曲率微扰具有相似的结构。高阶相互作用对于较小的声速平方变得越来越重要，也就是说，当理论接近GR时。这使得任何线性化分析无效，并且由于量子校正不可控制，因此在此限制下失去了任何可预测性。标量引力子的这种病态行为使人们对该理论的可投射版本的有效性产生了怀疑。
We confirm the recent claims that, in the infrared limit of Hořava-Lifshitz gravity, the scalar graviton becomes a ghost if the sound speed squared is positive on the flat de Sitter and Minkowski background. In order to avoid the ghost and tame the instability, the sound speed squared should be negative and very small, which means that the flow parameter λ should be very close to its General Relativity (GR) value. We calculate the cubic interactions for the scalar graviton which are shown to have a similar structure with those of the curvature perturbation in k-inflation models. The higher order interactions become increasing important for a smaller sound speed squared, that is, when the theory approaches GR. This invalidates any linearized analysis and any predictability is lost in this limit as quantum corrections are not controllable. This pathological behaviour of the scalar graviton casts doubt on the validity of the projectable version of the theory.