Lambda-determinants and domino-tilings
Abstract
Description
Consider the $2n$-by-$2n$ matrix $M=(m_{i,j})_{i,j=1}^{2n}$ with $m_{i,j} = 1$ for $i,j$ satisfying $|2i-2n-1|+|2j-2n-1| \leq 2n$ and $m_{i,j} = 0$ for all other $i,j$, consisting of a central diamond of 1's surrounded by 0's. When $n \geq 4$, the $λ$-determinant of the matrix $M$ (as introduced by Robbins and Rumsey) is not well-defined. However, if we replace the 0's by $t$'s, we get a matrix whose $λ$-determinant is well-defined and is a polynomial in $λ$ and $t$. The limit of this polynomial as $t \to 0$ is a polynomial in $λ$ whose value at $λ=1$ is the number of domino tilings of a $2n$-by-$2n$ square.
4 pages; to appear in a special issue of Advances in Applied Mathematics honoring David P. Robbins
4 pages; to appear in a special issue of Advances in Applied Mathematics honoring David P. Robbins