Constraining spacetime torsion with the Moon and Mercury

TL;DR

This paper investigates the effects of spacetime torsion within Einstein-Cartan theory on planetary and lunar orbits, using observational data to constrain torsion parameters and test deviations from General Relativity.

Contribution

It extends the parametrized torsion framework to orbital dynamics and derives new constraints on torsion parameters from lunar and planetary data.

Findings

Constraints on torsion parameters from lunar laser ranging.

Constraints on torsion parameters from Mercury's perihelion data.

Demonstrates how torsion affects orbital precession and can be tested with existing measurements.

Abstract

We report a search for new gravitational physics phenomena based on Einstein-Cartan theory of General Relativity including spacetime torsion. Starting from the parametrized torsion framework of Mao, Tegmark, Guth and Cabi, we analyze the motion of test bodies in the presence of torsion, and in particular we compute the corrections to the perihelion advance and to the orbital geodetic precession of a satellite. We describe the torsion field by means of three parameters, and we make use of the autoparallel trajectories, which in general may differ from geodesics when torsion is present. We derive the equations of motion of a test body in a spherically symmetric field, and the equations of motion of a satellite in the gravitational field of the Sun and the Earth. We calculate the secular variations of the longitudes of the node and of the pericenter of the satellite. The computed secular variations show how the corrections to the perihelion advance and to the orbital de Sitter effect depend on the torsion parameters. All computations are performed under the assumptions of weak field and slow motion. To test our predictions, we use the measurements of the Moon geodetic precession from lunar laser ranging data, and the measurements of Mercury's perihelion advance from planetary radar ranging data. These measurements are then used to constrain suitable linear combinations of the torsion parameters.