Hardy Spaces and Boundary Conditions from the Ising Model
  Functions in Hardy spaces on multiply-connected domains in the plane are given an explicit characterization in terms of a boundary condition inspired by the two-dimensional Ising model. The key underlying property is the positivity of a certain operator constructed inductively on the number of components of the boundary. 
Cl\'ement Hongler and Duong Hong Phong
math.CV math-ph math.MP