Dilatonic probe, force balance and gyromagnetic ratio

Following the Papapetrou-Dixon-Wald procedure we derive the equation of mot ion for a dilatonic test body (probe) with the dilaton coupling alpha = roo t p/(2+p) in four dimension. Since the dilatonic freedom sometimes comes fr om extra dimensions, it is best to derive the EOM by a dimensional reductio n from (p + 4)-dimensions. We discuss about the force balance up to the gra vitational spin-spin interactions via the probe technique. The force balanc e condition yields the saturation of a Bogomol'nyi bound and the gyromagnet ic ratio of the test body. (C) 1999 Elsevier Science B.V. All rights reserv ed.