Slab percolation for the Ising model revisited

In this note, we give a new and short proof for a theorem of Bodineau stating that the slab percolation threshold ${\widehat{p}}_c$ for the FK-Ising model coincides with the standard percolation critical point $p_c$ in all dimensions $d\ge 3$. Both proofs rely on the positivity of the surface tension for $p>p_c$ proved by Lebowitz & Pfister. The key difference is that while Bodineau’s proof is based on a delicate dynamic renormalization inspired by the work of Barsky, Grimmett & Newman, our proof utilizes a technique of Benjamini & Tassion to prove the uniqueness of macroscopic clusters via sprinkling, which then implies percolation on slabs through a rather straightforward static renormalization.