Born-Infeld-Einstein Actions?
  We present some obvious physical requirements on gravitational avatars of non-linear electrodynamics and illustrate them with explicit determinantal Born-Infeld-Einstein models. A related procedure, using compensating Weyl scalars, permits us to formulate conformally invariant versions of these systems as well. 
S. Deser (Brandeis University) and G.W. Gibbons (Cambridge University)