Shape-dependent universality in percolation
  The shape-dependent universality of the excess percolation cluster number and cross-configuration probability on a torus is discussed. Besides the aspect ratio of the torus, the universality class depends upon the twist in the periodic boundary conditions, which for example are generally introduced when triangular lattices are used in simulations. 
Robert M. Ziff (1), Christian D. Lorenz (1), and Peter Kleban (2) ((1)   University of Michigan, (2) University of Maine)