Estimation for Entanglement Negativity of Free Fermions
  In this letter we study the negativity of one dimensional free fermions. We derive the general form of the $\mathbb{Z}_{N}$ symmetric term in moments of the partial transposed (reduced) density matrix, which is an algebraic function of the end points of the system. Such a path integral turns out to be a convenient tool for making estimations for the negativity. 
Christopher P. Herzog and Yihong Wang
hep-th cond-mat.stat-mech quant-ph