Weak equivalence principle for selfgravitating bodies: A sieve for purely metric theories of gravity
Abstract
We propose the almostgeodesic motion of selfgravitating 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 wellposed variational formulation, this test singles out only the purely metric theories of gravity. This conclusion reproduces known results in the cases of general relativity (as well as with a cosmological constant term) and scalartensor theories, but extends also to debated or unknown scenarios, such as the f(R) and LanczosLovelock theories. We thus provide new tools going beyond the standard methods, where the latter turn out to be inconclusive or inapplicable.
 Publication:

Physical Review D
 Pub Date:
 April 2014
 DOI:
 10.1103/PhysRevD.89.084053
 arXiv:
 arXiv:1401.0030
 Bibcode:
 2014PhRvD..89h4053D
 Keywords:

 04.20.Cv;
 04.50.Kd;
 Fundamental problems and general formalism;
 Modified theories of gravity;
 General Relativity and Quantum Cosmology
 EPrint:
 17 pages, no figures. Tiny modifications to match the published version