Tests of Gravity with Future Space-Based Experiments

TL;DR

Future space-based experiments will significantly improve tests of gravity, constraining alternative theories like chameleon, symmetron, and galileon models through precise measurements of gravitational effects.

Contribution

This paper estimates the potential bounds on alternative gravity theories from upcoming space-based experiments, highlighting their ability to test and constrain these models.

Findings

Space experiments will tighten constraints on the PPN parameter γ.

Laser ranging to Phobos will set new limits on galileon theories.

Upcoming tests will improve understanding of the inverse-square law and equivalence principles.

Abstract

Future space-based tests of relativistic gravitation-laser ranging to Phobos, accelerometers in orbit, and optical networks surrounding Earth-will constrain the theory of gravity with unprecedented precision by testing the inverse-square law, the strong and weak equivalence principles, and the deflection and time-delay of light by massive bodies. In this paper, we estimate the bounds that could be obtained on alternative gravity theories that use screening mechanisms to suppress deviations from general relativity in the solar system: chameleon, symmetron, and galileon models. We find that space-based tests of the parameterized post-Newtonian parameter $\gamma$ will constrain chameleon and symmetron theories to new levels in the solar system, and that tests of the inverse-square law using laser ranging to Phobos will provide the most stringent constraints on galileon theories to date. We end by discussing the potential for constraining these theories using upcoming tests of the weak equivalence principle, and conclude that further theoretical modeling is required in order to fully utilize the data.