Monte Carlo calculations of the finite density Thirring model
  We present results of the numerical simulation of the two-dimensional Thirring model at finite density and temperature. The severe sign problem is dealt with by deforming the domain of integration into complex field space. This is the first example where a fermionic sign problem is solved in a quantum field theory by using the holomorphic gradient flow approach, a generalization of the Lefschetz thimble method. 
Andrei Alexandru, Gokce Basar, Paulo F. Bedaque, Gregory W. Ridgway,   and Neill C. Warrington
hep-lat