Reduction of a family of metric gravities
With highlights on conservation laws in metric formulations, consistency before dynamics, and a fresh view on the unity of Newtonian and Einsteinian gravity
Institut für Physik, Otto-von-Guericke-Universität, 39016, Magdeburg, Germany
* e-mail: Klaus.Kassner@ovgu.de
Accepted: 2 May 2019
Published online: 30 July 2019
A recent proposal by Shuler regarding a postulate-based derivation of a family of metrics describing the gravitational field outside a static spherically symmetric mass distribution is reviewed. All of Shuler’s gravities agree with the Schwarzschild solution in the weak-field limit, but they differ in the strong-field domain, i.e., close enough to a sufficiently compact source of the field. It is found that the evoked postulates of i) momentum conservation and ii) consistency of field strength measurement are satisfied in all metric theories of gravity compatible with the Einstein equivalence principle, no matter what the form of the metric. Therefore, they cannot be used, within any correct deduction, to derive a particular metric. Shuler’s derivations are based on an inconsistent set of correspondences between local and distant measurements. Furthermore, it is shown here that out of the family of possible metrics given by Shuler only one member, the Schwarzschild metric, satisfies a standard relativistic generalization of Newton’s law of gravitation, suggesting the others to be unphysical.
© Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature, 2019