  We study the scaling of the Renyi and entanglement entropy of two disjoint
blocks of critical Ising models, as function of their sizes and separations. We
present analytic results based on conformal field theory that are
quantitatively checked in numerical simulations of both the quantum spin chain
and the classical two dimensional Ising model. Theoretical results match the
ones obtained from numerical simulations only after taking properly into
account the corrections induced by the finite length of the blocks to their
leading scaling behavior.
