Geometric representation of the 2D Antiferromagnetic Ising Model with   topological term at \theta=\pi
  We study the two-dimensional Antiferromagnetic Ising Model with an imaginary magnetic field i\theta at \theta=\pi. We use a new geometric algorithm which does not present a sign problem. This allows us to perform efficient numerical simulations of this system. 
V. Azcoiti, G. Cortese, E. Follana and M. Giordano
hep-lat