Dilaton gravity (with a Gauss-Bonnet term) derived from five-dimensional   Chern-Simons gravity
  We study the problem of boundary terms and boundary conditions for Chern-Simons gravity in five dimensions. We show that under reasonable boundary conditions one finds an effective field theory at the four-dimensional boundary described by dilaton gravity with a Gauss-Bonnet term. The coupling of matter is also discussed. 
Maximo Banados