Variation of Entanglement Entropy in Scattering Process
  In a scattering process, the final state is determined by an initial state and an S-matrix. We focus on two-particle scattering processes and consider the entanglement between these particles. For two types initial states; i.e., an unentangled state and an entangled one, we calculate perturbatively the change of entanglement entropy from the initial state to the final one. Then we show a few examples in a field theory and in quantum mechanics. 
I.Y. Park, Shigenori Seki, Sang-Jin Sin
hep-th