Localized gravity and higher curvature terms

We consider localization of gravity in smooth domain wall solutions of grav ity coupled to a scalar field with a generic potential in the presence of t he Gauss-Bonnet term. We discuss conditions on the scalar potential such th at domain wall solutions are non-singular. We point out that the presence o f the Gauss-Bonnct term does not allow flat solutions with localized gravit y that violate the weak energy condition. We also point out that in the pre sence of the Gauss-Bonnet term infinite tension flat domain walls violate p ositivity. In fact, for flat solutions unitarity requires that on the solut ion the scaler potential he bounded below. (C) 2000 Elsevier Science B.V. A ll rights reserved.