Constraints on unified theories from the experimental tests of the equivalence principle

The predictions of a general unified theory for the gravitational, electromagnetic and scalar field are compared with the results of the experimental tests of the equivalence principle. It is shown that the theoretical predictions do not disagree with experimental data provided that the coupling of the scalar to the electromagnetic field is suppressed by a factork 10^–3, or, alternatively, the scalar field is massive; in this case, a lower limit for its mass is obtained.