Modified Jordan-Brans-Dicke theory with scalar current and the Eddington-Robertson gamma-parameter

Abstract

The Jordan-Brans-Dicke theory of gravitation, which promotes the gravitational constant to a dynamical scalar field, predicts a value for the Eddington-Robertson post-Newtonian parameter gamma that is significantly different from the general relativistic value of unity. This contradicts precision solar system measurements that tightly constrain gamma around 1. We consider a modification of the theory, in which the scalar field is sourced explicitly by matter. We find that this leads to a modified expression for the gamma-parameter. In particular, a specific choice of the scalar current yields gamma=1, just as in general relativity, while the weak equivalence principle is also satisfied. This result has important implications for theories that mimic Jordan-Brans-Dicke theory in the post-Newtonian limit in the solar system, including our scalar-tensor-vector modified gravity theory (MOG).

7 pages, accepted for publication in International Journal of Modern Physics D

References in corpus (4)

• f(R) Gravity and scalar-tensor theory
• Field-theoretical formulations of MOND-like gravity
• Fundamental parameter-free solutions in Modified Gravity
• A Modified Scalar-Tensor-Vector Gravity Theory and the Constraint on its Parameters

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• Post-Newtonian parameters and cosmological constant of screened modified gravity
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• The γ parameter in Brans-Dicke-like (light-)Scalar-Tensor theory with a universal scalar/matter coupling
• An FLRW Cosmology with a Chameleon Field
• Constraining runaway dilaton models using joint gravitational-wave and electromagnetic observations