On the quasi-linearity of the Einstein- "Gauss-Bonnet" gravity field equations

We review some properties of the Einstein-“Gauss-Bonnet” equations for gravity–also called the Einstein-Lanczos equations in five and six dimensions, and the Lovelock equations in higher dimensions. We illustrate, by means of simple Kaluza-Klein and brane cosmological models, some consequences of the quasi-linearity of these equations on the Cauchy problem (a point first studied by Yvonne Choquet-Bruhat), as well as on “junction conditions”.