On the mean Euler characteristic and mean Betti numbers of the Ising   model with arbitrary spin
  The behaviour of the mean Euler-Poincar\'{e} characteristic and mean Betti's numbers in the Ising model with arbitrary spin on $\mathbbm{Z}^2$ as functions of the temperature is investigated through intensive Monte Carlo simulations. We also consider these quantities for each color $a$ in the state space $S\_Q = \{- Q, - Q + 2, ..., Q \}$ of the model. We find that these topological invariants show a sharp transition at the critical point. 
Philippe Blanchard (BIBOS), Christophe Dobrovolny (MATH-PHY), Daniel   Gandolfo (CPT), Jean Ruiz (CPT)