Sandpiles and Dominos

  • Laura Florescu
  • Daniela Morar
  • David Perkinson
  • Nicholas Salter
  • Tianyuan Xu
Keywords: sandpiles, dominos


We consider the subgroup of the abelian sandpile group of the grid graph consisting of configurations of sand that are symmetric with respect to central vertical and horizontal axes. We show that the size of this group is (i) the number of domino tilings of a corresponding weighted rectangular checkerboard; (ii) a product of special values of Chebyshev polynomials; and (iii) a double-product whose factors are sums of squares of values of trigonometric functions. We provide a new derivation of the formula due to Kasteleyn and to Temperley and Fisher for counting the number of domino tilings of a $2m \times 2n$ rectangular checkerboard and a new way of counting the number of domino tilings of a $2m \times 2n$ checkerboard on a Möbius strip.

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