Entanglement Entropy of Black Shells
  We present a coherent account of how the entanglement interpretation, thermofield dynamical description and the brick wall formulations (with the ground state correctly identified) fit into a connected and self-consistent explanation of what Bekenstein-Hawking entropy is, and where it is located. 
J. Robel Arenas, J. Manuel Tejeiro
gr-qc hep-th