Pulsar Constraints on Screened Modified Gravity
We calculate the rate of energy loss from compact astrophysical objects due to a scalar field in screened modified gravity models of the chameleon, dilaton and symmetron types. For binary systems, this is related to the time drift of the orbital period complementing the effect due to gravitational wave emission in General Relativity. The scalar energy flow is sensitive to the time evolution of the scalar field on cosmological scales and the screened gravitational charge of the massive bodies, eventually leading to a dependence on the range of the scalar interaction on cosmological scales in the present Universe. Using the Hulse-Taylor binary pulsar, the double pulsar PSR J0737-3039 and the pulsar-white dwarf system PSR J1738+033, we find the most stringent observational bound on the range $λ$ of the scalar field $λ ≤sssim 1$ Mpc.