DYNAMICS OF A SELF-GRAVITATING THIN-STRING IN SCALAR-TENSOR THEORIES OF GRAVITATION

We examine the dynamics of a self-gravitating string in the scalar-ten sor theories of gravitation by considering it to be described by a thi n tube of matter. For a class of solutions, we obtain in the generic c ase that the extrinsic curvature of the worldsheet of the central line is null in the limit where the radius of the string tends to zero. Ho wever, if we impose a specific constraint on the behaviour of the solu tion then we End that only the mean curvature of the worldsheet of the central line vanishes, which is just the Nambu-Goto dynamics. This an alysis can include the massless dilatonic theories of gravity.