Ghosts, instabilities, and superluminal propagation in modified gravity models
Ghosts, instabilities, and superluminal propagation in modified gravity models
复制标题
修正重力模型中的幽灵、不稳定性和超光速传播
DOI：
10.1088/1475-7516/2006/08/005
复制
发表时间：
2006
影响因子：
6.4
通讯作者：
M. Trodden
中科院分区：
文献类型：
--
作者：
Antonio De Felice;M. Hindmarsh;M. Trodden
我们考虑修正的引力模型，涉及四阶曲率不变量的逆幂。利用这些模型与标量场耦合不变量线性组合理论的等价性，我们研究了传播模式的性质。即使在场方程中的四阶导数项消失的情况下，我们发现，二阶导数项可以引起鬼，不稳定性和超光速传播速度。我们建立的理论必须满足的条件，以避免这些问题在弗里德曼背景下，并表明，晚时间吸引子解决方案一般表现出superluminally传播张量或标量模式。
We consider modified gravity models involving inverse powers of fourth order curvature invariants. Using these models’ equivalence to the theory of a scalar field coupled to a linear combination of the invariants, we investigate the properties of the propagating modes. Even in the case for which the fourth derivative terms in the field equations vanish, we find that the second derivative terms can give rise to ghosts, instabilities, and superluminal propagation speeds. We establish the conditions which the theories must satisfy in order to avoid these problems in Friedmann backgrounds, and show that the late time attractor solutions generically exhibit superluminally propagating tensor or scalar modes.