Modified Segre conjecture for fat points in arbitrary position

From papers

Fix integers d2d\ge 2 and n>2n>2. Let SPnS\subseteq {\mathbb P}^n be a finite collection of ss points, fix integers m1,,msm_1,\dots,m_s, and set

Z:=i=1smipi.Z:=\sum_{i=1}^s m_i p_i.

Let w(Z)\operatorname{w}(Z) be the total weight of ZZ, and for a linear subspace LPnL\subseteq {\mathbb P}^n let wL(Z)\operatorname{w}_L(Z) be the sum of the multiplicities of the points lying in LL. Modified Segre conjecture. Then h1(IZ(d))=0h^1(\mathcal I_Z(d))=0 if all the following conditions hold: w(Z)nd+1\operatorname{w}(Z)\le nd+1; wL(Z)d+1\operatorname{w}_L(Z)\le d+1 for each line LPnL\subseteq {\mathbb P}^n; and, for every integer r=2,,n1r=2,\dots,n-1 and every rr-dimensional linear subspace LPnL\subseteq {\mathbb P}^n, wL(Z)rd+2\operatorname{w}_L(Z)\le rd+2, with the additional assumption h1(L,IZL(d))=0h^1(L,\mathcal I_{Z\cap L}(d))=0 whenever wL(Z)=rd+2\operatorname{w}_L(Z)=rd+2. This conjecture modifies Segre's conjecture for points in arbitrary position by imposing weight conditions on linear subspaces and a boundary cohomology condition. The supplied text presents examples and evidence but no resolution, so the conjecture remains open.

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Sources & referencesView supporting material

Primary source

Edoardo Ballico, Olivia Dumitrescu and Elisa Postinghel, “On Segre's bound for fat points in P^n”, arXiv:1504.05151 (2015).

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