Abstract
We study linear metric perturbations around a spherically symmetric static spacetime for general theories, where is the Ricci scalar and is the Gauss-Bonnet term. We find that, unless the determinant of the Hessian of is zero, even-type perturbations have a ghost for any multipole mode. In order for these theories to be plausible alternatives to general relativity, the theory should satisfy the condition that the ghost is massive enough to effectively decouple from the other fields. We study the requirement on the form of which satisfies this condition. We also classify the number of propagating modes both for the odd-type and the even-type perturbations and derive the propagation speeds for each mode.
- Received 16 February 2011
DOI:https://doi.org/10.1103/PhysRevD.83.104035
© 2011 American Physical Society