Weakened Minimal Resolution Conjecture for points in P1×P2\mathbb P^1\times\mathbb P^2

From papers

Let N2N\geq 2 be an integer, and let U(P1×P2)NU\subseteq(\mathbb P^1\times\mathbb P^2)^N be a dense open subset. For (P1,P2,,PN)U(P_1,P_2,\dots,P_N)\in U, set X={P1,,PN}X=\{P_1,\dots,P_N\}, and let S/IXS/I_X be its coordinate ring with bigraded Betti numbers β1,(i,j)\beta_{1,(i,j)}. For a matrix HH indexed by (i,j)Z2(i,j)\in\mathbb Z^2, write

DH=(ΔC)2(ΔR)3H.DH=(\Delta^C)^2(\Delta^R)^3H.

Let HXH_X be the Hilbert matrix of XX.

Weakened Minimal Resolution Conjecture. The set XX has a generic Hilbert matrix as in the source definition, and, for every fixed (i,j)>(0,0)(i,j)>(0,0), one has β1,(i,j)>0\beta_{1,(i,j)}>0 if and only if

DHX(i,j)<0andDHX(i,j)0DH_X(i,j)<0\quad\text{and}\quad DH_X(i',j')\leq 0

for all (i,j)(i,j)(i',j')\leq(i,j) with (i,j)(0,0)(i',j')\neq(0,0). Whenever this condition holds,

β1,(i,j)=DHX(i,j).\beta_{1,(i,j)}=-DH_X(i,j).

This is a weakened version of the Minimal Resolution Conjecture for sufficiently general points in P1×P2\mathbb P^1\times\mathbb P^2: it only prescribes the first Betti numbers, but that control is intended to determine enough of the resolution to establish the paper's virtual-resolution results. The parser supplies no evidence that the conjecture has been resolved, so its status remains open.

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Sources & referencesView supporting material

Primary source

Isidora Bailly-Hall, Christine Berkesch, Karina Dovgodko, Sean Guan, Saisudharshan Sivakumar and Jishi Sun, “On virtual resolutions of points in a product of projective spaces”, arXiv:2402.12495 (2024).

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