Area law of the entropy in the critical gravity
  The entropy of the Schwarzschild-anti de Sitter black hole in the recently proposed four-dimensional critical gravity is trivial in the Euclidean action formulation, while it is expressed by the area law in terms of the brick wall method given by 't Hooft. To resolve this issue, we relate the Euclidean action formulation to the brick wall method semiclassically, and show that the entropy of the black hole can be expressed by the area law at the critical point. 
Edwin J. Son, Myungseok Eune, Wontae Kim
hep-th gr-qc