Weak-field limit of Kaluza-Klein models with spherical compactification: experimental constraints

TL;DR

This paper examines six-dimensional Kaluza-Klein models with spherical compactification, analyzing their gravitational behavior and experimental constraints, and finds that certain parameter choices align with observed gravitational tests.

Contribution

It provides the first detailed analysis of weak-field gravitational tests for this specific Kaluza-Klein model with spherical internal space and derives experimental bounds on model parameters.

Findings

Yukawa-type corrections to Newtonian potential for certain parameters

Model satisfies Solar system gravitational tests with high accuracy

Stable compactification achieved for positive internal space equation of state parameter 

Abstract

We investigate the classical gravitational tests for the six-dimensional Kaluza-Klein model with spherical (of a radius $a$) compactification of the internal space. The model contains also a bare multidimensional cosmological constant $\Lambda_6$. The matter, which corresponds to this ansatz, can be simulated by a perfect fluid with the vacuum equation of state in the external space and an arbitrary equation of state with the parameter $\omega_1$ in the internal space. For example, $\omega_1=1$ and $\omega_1=2$ correspond to the monopole two-forms and the Casimir effect, respectively. In the particular case $\Lambda_6=0$, the parameter $\omega_1$ is also absent: $\omega_1=0$. In the weak-field approximation, we perturb the background ansatz by a point-like mass. We demonstrate that in the case $\omega_1>0$ the perturbed metric coefficients have the Yukawa type corrections with respect to the usual Newtonian gravitational potential. The inverse square law experiments restrict the parameters of the model: $a/\sqrt{\omega_1}\lesssim 6\times10^{-3}\ {{cm}}$. Therefore, in the Solar system the parameterized post-Newtonian parameter $\gamma$ is equal to 1 with very high accuracy. Thus, our model satisfies the gravitational experiments (the deflection of light and the time delay of radar echoes) at the same level of accuracy as General Relativity. We demonstrate also that our background matter provides the stable compactification of the internal space in the case $\omega_1>0$. However, if $\omega_1=0$, then the parameterized post-Newtonian parameter $\gamma=1/3$, which strongly contradicts the observations.