Geodesics and cosmic expansion

Abstract

In this paper it is my goal to show how the solutions for the geodesics in some model of spacetime can be used to provide a locally testable result, which could be used experimentally to verify or to deny some cosmological model. Thus by studying planetary orbits we obtain certain bounds on parameters in the equations pertaining to cosmological expansion. We also examine the geodesic equations for brane world cosmological models order to judge the suitability of these models in describing our universe. Brane worlds are those models of a universe with extra dimensions, where all matter is embedded in a brane, or a hypersurface, corresponding to the observed properties of our universe. These models are akin to the higher dimensional models generated by string theory, except that the "rolled up" dimensions are replaced by extended dimensions, under the constraint that matter lie in the brane.