Six-vertex model as a Grassmann integral, one-point function, and the arctic ellipse

We formulate the six-vertex model with domain wall boundary conditions in terms of an integral over Grassmann variables. Relying on this formulation, we propose a method of calculation of correlation functions of the model for the case of the weights satisfying the free-fermion condition. We consider here in details the one-point correlation function describing the probability of a given state on arbitrary edge of the lattice, or, – polarization. We show that in the thermodynamic limit, performed such that the lattice is scaled to the square of unit side length, this function exhibits the “arctic ellipse” phenomenon, in agreement with previous studies on random domino tilings of Aztec diamonds: it approaches its limiting values outside of an ellipse inscribed into this square, and takes continuously intermediate values inside the ellipse. We derive also scaling properties of the one-point function in the vicinity of an arbitrary point of the arctic ellipse and in the vicinities of the points where the ellipse touches the boundary.