Foundations of Physics

, Volume 42, Issue 2, pp 209–214 | Cite as

A Brief Remark on Energy Conditions and the Geroch-Jang Theorem

  • James Owen Weatherall


The status of the geodesic principle in General Relativity has been a topic of some interest in the recent literature on the foundations of spacetime theories. Part of this discussion has focused on the role that a certain energy condition plays in the proof of a theorem due to Bob Geroch and Pong-Soo Jang [“Motion of a Body in General Relativity.” Journal of Mathematical Physics 16(1) (1975)] that can be taken to make precise the claim that the geodesic principle is a theorem, rather than a postulate, of General Relativity. In this brief note, I show, by explicit counterexample, that not only is a weaker energy condition than the one Geroch and Jang state insufficient to prove the theorem, but in fact a condition still stronger than the one that they assume is necessary.


Inertial motion General relativity Geroch-Jang theorem Energy condition Geodesic principle 


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© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.Logic and Philosophy of ScienceUniversity of CaliforniaIrvineUSA

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