Testing for gravitationally preferred directions using the lunar orbit

Abstract

As gravity is a long-range force, it is {\it a priori} conceivable that the Universe's global matter distribution select a preferred rest frame for local gravitational physics. At the post-Newtonian approximation, the phenomenology of preferred-frame effects is described by two parameters, ${\alpha }_1$ and ${\alpha }_2$, the second of which is already very tightly constrained. Confirming previous suggestions, we show through a detailed Hill-Brown type calculation of a perturbed lunar orbit that lunar laser ranging data have the potential of constraining ${\alpha }_1$ at the $10^{-4}$ level. It is found that certain retrograde planar orbits exhibit a resonant sensitivity to external perturbations linked to a fixed direction in space. The lunar orbit being quite far from such a resonance exhibits no significant enhancement due to solar tides. Our Hill-Brown analysis is extended to the perturbation linked to a possible differential acceleration toward the galactic center. It is, however, argued that there are strong {\it a priori} theoretical constraints on the conceivable magnitude of such an effect.

20 pages, Revtex, submitted to Phys Rev D

References in corpus (5)

• The String Dilaton and a Least Coupling Principle
• String theory and gravity
• The Equivalence Principle and the Moon
• A Tighter Test of Local Lorentz Invariance using PSR J2317+1439
• Testing for Preferred-Frame Effects in Gravity with Artificial Earth Satellites

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• Space-based tests of gravity with laser ranging
• Spatial variation of fundamental couplings and Lunar Laser Ranging
• The Confrontation between General Relativity and Experiment: A 1998 Update
• Laser Ranging to the Moon, Mars and Beyond
• Gravitation, experiment and cosmology