http://arxiv.org/abs/2212.12494
We investigate the conditions under which cubic gravity is healthy and viable at the perturbation level. We perform a detailed analysis of the scalar and tensor perturbations. After showing that no instabilities appear, we impose the requirement that the two scalar potentials, whose ratio is the post-Newtonian parameter $\gamma$, should deviate only minimally form general relativity. Additionally, concerning the tensor perturbations we impose satisfaction of the LIGO-VIRGO and Fermi Gamma-ray Burst observations, and thus we result to a gravitational-wave equation with gravitational-wave speed equal to the speed of light, and where the only deviation from general relativity appears in the dispersion relation. Furthermore, we show that cubic gravity exhibits an effective Newton’s constant that depends on the model parameter, on the background evolution, and on the wavenumber scale. Hence, by requiring its deviation from the standard Newton’s constant to be within observational bounds we extract the constraints on the single coupling parameter $\beta$.
P. Asimakis, S. Basilakos and E. Saridakis
Mon, 26 Dec 22
4/39
Comments: 9 pages, 2 figures