Active mass in relativistic gravity - Theoretical interpretation of the Kreuzer experiment

Abstract

A 1966 experiment performed by Kreuzer set an upper limit of 5 parts in 10/sup 5/ on the difference in the ratio of active to passive mass between fluorine and bromine. (Active mass of a body is the mass that generates gravity, while passive mass is the mass that responds to gravity.) A parametrized post-Newtonian formalism is introduced for the spacetime metric of a system of charged point particles using parameters (..gamma..,..beta.., ..cap alpha../sub 1/, ..cap alpha../sub 2/, ..cap alpha../sub 3/, zeta/sub 1/, zeta/sub 2/, zeta/subW/, epsilon/sub 1/, epsilon/sub 2/, epsilon/sub 3/) whose values vary from gravitation theory to gravitation theory. The prediction of this formalism for the active gravitational masses of fluorine and bromine nuclei is compared with the results of the Kreuzer experiment and place an upper limit on a combination of these PPN parameters. By making a detailed comparison of the point-mass formalism with the standard perfect-fluid PPN formalism, it is shown that for the theories of gravitation whose perfect-fluid equations are blind to the different forms of internal energy and pressure in the fluid, the perfect-fluid PPN parameters must satisfy the constraint zeta/sub 3/+2zeta/sub 4/-..cap alpha../sub 3/-2/3zeta/sub 1/ =0. For such theories it is demonstrated thatmore » the Kreuzer experiment imposes the limit vertical-barzeta/sub 3/vertical-bar<0.06. Any theory of gravity that possesses post-Newtonian integral conservation laws for total momentum automatically agrees with the Kreuzer experiment. (AIP)« less