Weak field limit of higher dimensional massive Brans-Dicke gravity: Observational constraints

Abstract

We consider higher-dimensional massive Brans-Dicke theory with Ricci-flat internal space. The background model is perturbed by a massive gravitating source which is pressureless in the external (our space) but has an arbitrary equation-of-state parameter $\mathrm{\ensuremath{\Omega}}$ in the internal space. We obtain the exact solution of the system of linearized equations for the perturbations of the metric coefficients and scalar field. For a massless scalar field, relying on the fine-tuning between the Brans-Dicke parameter $\ensuremath{\omega}$ and $\mathrm{\ensuremath{\Omega}}$, we demonstrate that (i) the model does not contradict gravitational tests relevant to the parameterized post-Newtonian parameter $\ensuremath{\gamma}$, and (ii) the scalar field is not ghost in the case of nonzero $|\mathrm{\ensuremath{\Omega}}|\ensuremath{\sim}O(1)$ along with the natural value $|\ensuremath{\omega}|\ensuremath{\sim}O(1)$. In the general case of a massive scalar field, the metric coefficients acquire the Yukawa correction terms, where the Yukawa mass scale $m$ is defined by the mass of the scalar field. For the natural value $\ensuremath{\omega}\ensuremath{\sim}O(1)$, the inverse-square-law experiments impose the following restriction on the lower bound of the mass: $m\ensuremath{\gtrsim}1{0}^{\ensuremath{-}11}\text{ }\text{ }\mathrm{GeV}$. The experimental constraints on $\ensuremath{\gamma}$ require that $\mathrm{\ensuremath{\Omega}}$ be extremely close to $\ensuremath{-}1/2$.