A Tighter Constraint on post-Newtonian Gravity using Millisecond Pulsars

Some theories of gravity predict the existence of preferred-frame effects and violations of conservation of energy and momentum. General relativity predicts no such effects. In the parameterised post-Newtonian (PPN) formalism, the parameter, \al3 $\equiv 0$ if these effects do not exist. The period derivatives ($\dot{P}$) of millisecond pulsars (MSPs) are used to more tightly constrain these effects by showing that $\mathrm{\mid }$\al3$\mathrm{\mid }$ $<5\times {10}^{-16}$.