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arXiv · 1401.0030

Weak equivalence principle for self-gravitating bodies: A sieve for purely metric theories of gravity

Eolo Di Casola·Stefano Liberati·Sebastiano Sonego
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Abstract

We propose the almost-geodesic motion of self-gravitating test bodies as a possible selection rule among metric theories of gravity. Starting from a heuristic statement, the "gravitational weak equivalence principle", we build a formal, operative test able to probe the validity of the principle for any metric theory of gravity, in an arbitrary number of spacetime dimensions. We show that, if the theory admits a well-posed variational formulation, this test singles out only the purely metric theories of gravity. This conclusion reproduces known results in the cases of general relativity (also with a cosmological constant term), and scalar-tensor theories, but extends also to debated or unknown scenarios, such as f(R) and Lanczos-Lovelock theories. We thus provide new tools going beyond the standard methods, where the latter turn out to be inconclusive or inapplicable.

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Eolo Di Casola, Stefano Liberati, Sebastiano Sonego. 2014-04-11. Weak equivalence principle for self-gravitating bodies: A sieve for purely metric theories of gravity. https://doi.org/10.1103/physrevd.89.084053

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