Symmetric Orbifolds and Entanglement Entropy for Primary Excitations in   Two Dimensional CFT
  We use the techniques in symmetric orbifolding to calculate the Entanglement Entropy of a single interval in a two dimensional conformal field theory on a circle which is excited to a pure highest weight state. This is achieved by calculating the Reney Entropy which is found in terms of a 2n-point function of primary operators, n being the replica number. 
Amir Esmaeil Mosaffa
hep-th cond-mat.stat-mech