Gravity Tests and the Pioneer Anomaly

Abstract

Experimental tests of gravity performed in the solar system show a good agreement with general relativity. The latter is however challenged by the Pioneer anomaly which might be pointing at some modification of gravity law at ranges of the order of the size of the solar system. We introduce a metric extension of general relativity which, while preserving the equivalence principle, modifies the coupling between curvature and stress tensors and, therefore, the metric solution in the solar system. The "post-Einsteinian extension" replaces Newton gravitation constant by two running coupling constants, which depend on the scale and differ in the sectors of traceless and traced tensors, so that the metric solution is characterized by two gravitation potentials. The extended theory has the capability to preserve compatibility with gravity tests while accounting for the Pioneer anomaly. It can also be tested by new experiments or, maybe, by having a

The Pioneer Anomaly

“…A modification of the gravitational field equations for a metric theory of gravity, by introducing a momentum-dependent linear relation between the Einstein tensor and the energy-momentum tensor, has been developed by Jaekel and Reynaud [147,148,149,150,151] and was shown to be able to account for a P . The authors identify two sectors, characterized by the two potentials…”