Planetary motion on an expanding locally anisotropic background

Abstract

In this work are computed analytical solutions for orbital motion on a background described by an Expanding Locally Anisotropic (ELA) metric ansatz. This metric interpolates between the Schwarzschild metric near the central mass and the Robertson-Walker metric describing the expanding cosmological background far from the central mass allowing for a fine-tuneable covariant parameterization of gravitational interactions corrections in between these two asymptotic limits. In particular it is shown that the decrease of the Sun's mass by radiation emission plus the General Relativity corrections due to the ELA metric background with respect to Schwarzschild backgrounds can be mapped to the reported yearly variation of the gravitational constant $\dot{G}$ through Kepler's third law. Based on the value of the heuristic fit corresponding to the more recent heliocentric ephemerides of the Solar System are derived bounds for the value of a constant parameter $\alpha_0$ for the ELA metric as well as the maximal corrections to perihelion advance and orbital radii variation within this framework. Hence it is shown that employing the ELA metric as a functional covariant parameterization to model gravitational interactions corrections within the Solar System allows to maintain the measurement projection standards constant over time, specifically both the Astronomical Unit ($AU$) and the Gravitational constant ($G$). Also it is noted that the effect obtained is not homogeneous for all planetary orbits consistently with the diversity of estimates in the literature obtained assuming Schwarzschild backgrounds.