Polynomial product formula conjecture for the generalized Aztec-diamond matrix

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Let A(k,t)A(k,t) be the skew-symmetric matrix whose entries satisfy

{a1,j=t,j>1,ai,j=ai−1,j+ai,j−1+ai−1,j−1,j>i+1,i>1,ai,j=ai−1,j+ai−1,j−1+k(−1)i−1,j=i+1,i>1,ai,j=−aj,i,j≤i.\begin{cases} a_{1,j}=t, & j>1,\\ a_{i,j}=a_{i-1,j}+a_{i,j-1}+a_{i-1,j-1}, & j>i+1,\quad i>1,\\ a_{i,j}=a_{i-1,j}+a_{i-1,j-1}+k(-1)^{i-1}, & j=i+1,\quad i>1,\\ a_{i,j}=-a_{j,i}, & j\leq i. \end{cases}

Write A[2n](k,t)A_{[2n]}(k,t) for its leading 2n×2n2n\times 2n principal submatrix, and let pf\mathsf{pf} denote the Pfaffian.

Generalized product formula conjecture. There exists a sequence of polynomials on(k,t)∈Z[k,t]o_n(k,t)\in\mathbb{Z}[k,t] such that

pf(A[2n](k,t))=t on−1(k,t)on(k,t).\mathsf{pf}(A_{[2n]}(k,t))=t\,o_{n-1}(k,t)o_n(k,t).

The conjecture has been checked by computer up to n=25n=25. Setting k=t=2k=t=2 recovers the preceding product formula conjecture, while a proof for general kk and tt remains open.

References

Primary source

Yi-Lin Lee, “Off-diagonally symmetric domino tilings of the Aztec diamond”, arXiv:2303.02750 (2023).

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