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Authors: Alexander Torres-Gomez, Kirill Krasnov

Date: 12 Nov 2008

Abstract: We revisit a propagating torsion gravity theory obtained by introducing a field coupled to the topological term in the first-order Einstein-Cartan action. The resulting theory has second order field equations, no adjustable coupling constants, and one more propagating degree of freedom as compared to general relativity. Thus, one might suspect that it should be easily ruled out by e.g. the solar system tests. To see whether this is the case, we obtain the spherically-symmetric solution of the theory, and show that it is characterized by the usual mass and an additional parameter. To our great surprise we find that the leading order corrections to the usual Newtonian behaviour are exactly as in general relativity, and, in particular, are independent of the new parameter. Thus, the theory passes the classical gravity tests. The analysis of the global structure of the solution leads to yet another surprising feature of the theory: the spherically-symmetric solution is never a black hole. One either has a naked curvature singularity or a wormhole solution connecting two asymptotic regions.

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