Justin Alsing, Emanuele Berti, Clifford Will, Helmut Zaglauer
We derive the equations of motion, the periastron shift, and the
gravitational radiation damping for quasicircular compact binaries in a massive
variant of the Brans-Dicke theory of gravity. We also study the Shapiro time
delay and the Nordtvedt effect in this theory. By comparing with recent
observational data, we put bounds on the two parameters of the theory: the
Brans-Dicke coupling parameter \omega_{BD} and the scalar mass m_s. We find
that the most stringent bounds come from Cassini measurements of the Shapiro
time delay in the Solar System, that yield a lower bound \omega_{BD}>40000 for
scalar masses m_s<2.5x10^{-20} eV, to 95% confidence. In comparison,
observations of the Nordtvedt effect using Lunar Laser Ranging (LLR)
experiments yield \omega_{BD}>1000 for m_s<2.5x10^{-20} eV. Observations of the
orbital period derivative of the quasicircular white dwarf-neutron star binary
PSR J1012+5307 yield \omega_{BD}>1250 for m_s<10^{-20} eV. A first estimate
suggests that bounds comparable to the Shapiro time delay may come from
observations of radiation damping in the eccentric white dwarf-neutron star
binary PSR J1141-6545, but a quantitative prediction requires the extension of
our work to eccentric orbits.
View original:
http://arxiv.org/abs/1112.4903
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