Crossing probability and number of crossing clusters in off-critical   percolation
  We consider two-dimensional percolation in the scaling limit close to criticality and use integrable field theory to obtain universal predictions for the probability that at least one cluster crosses between opposite sides of a rectangle of sides much larger than the correlation length and for the mean number of such crossing clusters. 
Gesualdo Delfino and Jacopo Viti
hep-th cond-mat.stat-mech