The symmetry conjecture for determinants of punctured-hexagon enumeration matrices

Let a=ba=b and α=β\alpha=\beta, so the punctured hexagon Ha,a,c,α,α,γH_{a,a,c,\alpha,\alpha,\gamma} is symmetric. Let AA, CC, and MM be the parameters associated with this hexagon, let Na,b,c,α,β,γN_{a,b,c,\alpha,\beta,\gamma} be its enumeration matrix, and let H\mathcal{H} denote the hyperfactorial function. If cc or γ\gamma is even, then

detNa,b,c,α,β,γ=(1)MC2×H(M+C)H(M+γ)H(M+A+C2)H(M+A+C2)H(M+2A+C)H(M+2A)H2(M+A+C)H2(M+C+γ2)\det N_{a,b,c,\alpha,\beta,\gamma}=(-1)^{M\left\lceil\frac{C}{2}\right\rceil}\times\frac{\mathcal{H}(M+C)\mathcal{H}(M+\gamma)\mathcal{H}(M+A+\left\lfloor\frac{C}{2}\right\rfloor)\mathcal{H}(M+A+\left\lceil\frac{C}{2}\right\rceil)\mathcal{H}(M+2A+C)}{\mathcal{H}(M+2A)\mathcal{H}^2(M+A+C)\mathcal{H}^2\left(M+\frac{C+\gamma}{2}\right)} ×H(M2)H(M2+A)H(M2+C+γ2)H(M2+A+Cγ2)H(M+C2)H(M+γ2)H(M+C2+A)H(Mγ2+A)\times\frac{\mathcal{H}\left(\left\lfloor\frac{M}{2}\right\rfloor\right)\mathcal{H}\left(\left\lfloor\frac{M}{2}\right\rfloor+A\right)\mathcal{H}\left(\left\lfloor\frac{M}{2}\right\rfloor+\frac{C+\gamma}{2}\right)\mathcal{H}\left(\left\lfloor\frac{M}{2}\right\rfloor+A+\frac{C-\gamma}{2}\right)}{\mathcal{H}\left(\left\lfloor\frac{M+C}{2}\right\rfloor\right)\mathcal{H}\left(\left\lfloor\frac{M+\gamma}{2}\right\rfloor\right)\mathcal{H}\left(\left\lfloor\frac{M+C}{2}\right\rfloor+A\right)\mathcal{H}\left(\left\lfloor\frac{M-\gamma}{2}\right\rfloor+A\right)} ×H(M2)H(M2+A)H(M2+C+γ2)H(M2+A+Cγ2)H(M+C2)H(M+γ2)H(M+C2+A)H(Mγ2+A)\times\frac{\mathcal{H}\left(\left\lceil\frac{M}{2}\right\rceil\right)\mathcal{H}\left(\left\lceil\frac{M}{2}\right\rceil+A\right)\mathcal{H}\left(\left\lceil\frac{M}{2}\right\rceil+\frac{C+\gamma}{2}\right)\mathcal{H}\left(\left\lceil\frac{M}{2}\right\rceil+A+\frac{C-\gamma}{2}\right)}{\mathcal{H}\left(\left\lceil\frac{M+C}{2}\right\rceil\right)\mathcal{H}\left(\left\lceil\frac{M+\gamma}{2}\right\rceil\right)\mathcal{H}\left(\left\lceil\frac{M+C}{2}\right\rceil+A\right)\mathcal{H}\left(\left\lceil\frac{M-\gamma}{2}\right\rceil+A\right)} ×H(Aγ2)H(C2)H(γ2)H(Aγ2)H(C2)H(γ2)H(γ)H2(A+Cγ2).\times\frac{\mathcal{H}\left(A-\left\lfloor\frac{\gamma}{2}\right\rfloor\right)\mathcal{H}\left(\left\lfloor\frac{C}{2}\right\rfloor\right)\mathcal{H}\left(\left\lfloor\frac{\gamma}{2}\right\rfloor\right)\mathcal{H}\left(A-\left\lceil\frac{\gamma}{2}\right\rceil\right)\mathcal{H}\left(\left\lceil\frac{C}{2}\right\rceil\right)\mathcal{H}\left(\left\lceil\frac{\gamma}{2}\right\rceil\right)}{\mathcal{H}(\gamma)\mathcal{H}^2\left(A+\frac{C-\gamma}{2}\right)}.

Moreover, the ideal Ia,a,c,α,α,γ=(xa,ya,zc,xαyαzγ)I_{a,a,c,\alpha,\alpha,\gamma}=(x^a,y^a,z^c,x^\alpha y^\alpha z^\gamma) has the weak Lefschetz property when the characteristic of KK is zero or at least 2A+C+M2A+C+M. This conjecture proposes a closed form for the symmetric case and a corresponding characteristic bound for the weak Lefschetz property.

Sources & referencesView supporting material

Primary source

David Cook and Uwe Nagel, “Enumerations deciding the weak Lefschetz property”, arXiv:1105.6062 (2011).

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