Nuclear Physics B
Low-energy limits of string theories suggest that gravity lagrangians should include quadratic and higheorder curvature terms, in the form of dimensionally continued Gauss-Bonnet densities. In an arbitrary number of dimensions, we consider the static, spherically symmetric solutions to the lowest order Gauss-Bonnet extended Einstein equations. We also find isotropic, homogeneous cosmological solutions with an ideal fluid source.
James T. Wheeler, Symmetric solutions to the Gauss-Bonnet extended Einstein equations, Nuclear Physics B, Volume 268, Issues 3-4, 12 May 1986, Pages 737-746, ISSN 0550-3213, 10.1016/0550-3213(86)90268-3.