Smirnov's fermionic observable away from criticality

Understand

In a recent and celebrated article, Smirnov [Ann.

• of Math.
• (2) 172 (2010) 1435-1467] defines an observable for the self-dual random-cluster model with cluster weight q = 2 on the square lattice $\mathbb{Z}^2$, and uses it to obtain conformal invariance in the scaling limit.
• We study this observable away from the self-dual point.