In general relativity, Gauss–Bonnet gravity, also referred to as Einstein–Gauss–Bonnet gravity, is a modification of the Einstein–Hilbert action to include the Gauss–Bonnet term (named after Carl Friedrich Gauss and Pierre Ossian Bonnet) This term is only nontrivial in 4+1D or greater, and as such, only applies to extra dimensional models. In 3+1D, it reduces to a topological surface term. This follows from the generalized Gauss–Bonnet theorem on a 4D manifold . In lower dimensions, it identically vanishes. More generally, we may consider