Random domino tilings of Aztec diamonds — frozen corners, liquid bulk
Jockusch-Propp-Shor (1998): In a random tiling of a 2n×2n Aztec diamond, the 4 corner regions freeze into regular tilings
as n→∞, with a sharp "arctic circle" boundary — exactly inscribed in the diamond. Inside: chaotic bulk fluctuations.
Colors represent 4 domino orientations (NW, NE, SW, SE frozen regions).