[0907.2186] Extracting the three- and four-graviton vertices from binary pulsars and coalescing binaries

Authors: Umberto Cannella, Stefano Foffa, Michele Maggiore, Hillary Sanctuary, Riccardo Sturani

Date: 13 Jul 2009

Abstract: Using a formulation of the post-Newtonian expansion in terms of Feynman graphs, we discuss how various tests of General Relativity (GR) can be translated into measurement of the three- and four-graviton vertices. In problems involving only the conservative dynamics of a system, a deviation of the three-graviton vertex from the GR prediction is equivalent, to lowest order, to the introduction of the parameter beta_{PPN} in the parametrized post-Newtonian formalism, and its strongest bound comes from lunar laser ranging, which measures it at the 0.02% level. Deviation of the three-graviton vertex from the GR prediction, however, also affects the radiative sector of the theory. We show that the timing of the Hulse-Taylor binary pulsar provides a bound on the deviation of the three-graviton vertex from the GR prediction at the 0.1% level. For coalescing binaries at interferometers we find that, because of degeneracies with other parameters in the template such as mass and spin, even a third-generation ground-based detector like EGO cannot provide significant constraints, while the observation of an extreme mass ratio inspiral at LISA would measure both the three- and the four-graviton vertices at roughly 10% level. For the four-graviton vertex this accuracy is interesting since solar system experiments and binary pulsars do not constrain it significantly.

abs pdf

Jul 14, 2009

0907.2186 (/preprints)
2009-07-14, 12:16 [edit]

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