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Authors: Nicolas Yunes, David N. Spergel

Date: 30 Oct 2008

Abstract: Gravitational parity violation is inherent in string theory, one effective model of which is Chern-Simons modified gravity. This effective theory introduces a parity-violating modification to the Einstein equations, whose magnitude depends on derivatives of the Chern-Simons coupling. In the dynamical formulation, this coupling is an evolving field that is sourced by spacetime curvature. We here calculate the Chern-Simons modification to the orbital evolution of a binary system of spinning compact objects in the weak-field. The ratio of the Chern-Simons correction to perigee precession to the general relativistic prediction is found to scale quadratically with the semi-major axis and inversely with the square of the object's radius. Binary pulsar systems are ideal to test this theory, since perigee precession can be measured with sub-degree accuracies and the semi-major axis is millions of times larger than the stellar radius. We find that observations of perigee precession from the double binary pulsar PSR J 0737-3039 A/B dramatically constrain the Chern-Simons coupling, M_(CS) := |\dot{\theta}|ˆ(-1) > 50 meV, approximately a hundred billion times better than Solar System tests.

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