Observations on entanglement entropy in massive QFT's
  We identify various universal contributions to the entanglement entropy for massive free fields. As well as the `area' terms found in [1], we find other geometric contributions of the form discussed in [2]. We also compute analogous contributions for a strongly coupled field theory using the AdS/CFT correspondence. In this case, we find the results for strong and weak coupling do not agree. 
Aitor Lewkowycz, Robert C. Myers and Michael Smolkin
hep-th