New tests of the strong equivalence principle using binary-pulsar data

One of the few experimental handles on the nonlinear properties of the gravitational interaction is to test the ``strong equivalence principle, '' i. e. , to test whether the ratio m₆ₑ₀ₕ₈ₓ₀ₓ₈₎₍₀₋/m₈₍₄ₑₓ₈₀₋ is 1 for self-gravitating bodies. We point out that existing observational data on the class of small-eccentricity long-orbital-period binary pulsars already provide a limit (namely m₆/m₈-11. 110^-2; 90% C. L. ) which goes beyond corresponding solar-system limits in probing strong-gravitational-field effects. Possible observational ways of improving this limit are suggested.