A-B droplets for a two-dimensional antiferromagnetic Ising model in external field H

The A-B site-bond percolation in the antiferromagnetic Ising model in an external field H is studied with the infinitesimal Migdal-Kadanoff renormalisation group. It is shown that for H=0 the clusters of holes and particles diverge at the Ising critical point K=Kc with the bond concentration pB in the range 1-exp(- mod Kc mod /2)<or=PB<or=1 as in the Coniglio-Klein model. For H not=0 the thermal antiferromagnetic critical line coincides with the percolation lines for a wider range of pB, i.e. pBmin(K)<or=pB(K)<or=1 where pBmin(K)<1-exp(- mod K mod /2).