ENTROPY OF FOLDING OF THE TRIANGULAR LATTICE

The problem of counting the different ways of folding the planar trian gular lattice is shown to be equivalent to that of counting the possib le 3-colourings of its bonds, a dual version of the 3-colouring proble m of the hexagonal lattice solved by Baxter. The folding entropy log q per triangle is thus given by Baxter's formula q = square-root 3 GAMM A(1/3)3/2/2pi = 1.2087....