Vanishing and global-generation conjecture for divisors on the resolved fourfold

Let X84X^4_8 be projective four-space blown up at eight general points. Let X84^\widehat{X^4_8} be obtained by blowing up the points, Weyl lines, and Weyl planes in the base locus of an effective divisor DD, and let D~\widetilde{D} be its proper transform. Let CC range over Weyl curves, and let wdim(D)\operatorname{wdim}(D) denote the Weyl expected dimension defined from the Euler characteristic and the multiplicities of Weyl cycles in the base locus.

Vanishing and global-generation conjecture. For every effective divisor DD on X84^\widehat{X^4_8}:

  1. If DC1D\mathbin{\cdot}C\geq -1 for every Weyl curve CC, then
H1(Xs4,OXs4(D))=0.H^1(X^4_s,\mathcal{O}_{X^4_s}(D))=0.
  1. One has
h0(D)=wdim(D)+r=13(1)r+1hr(D~).h^0(D)=\operatorname{wdim}(D)+\sum_{r=1}^{3}(-1)^{r+1}h^r(\widetilde{D}).
  1. For every r1r\geq1,
hr(D~)=0.h^r(\widetilde{D})=0.
  1. Moreover, D~\widetilde{D} is globally generated on X84^\widehat{X^4_8}.

This packages the source's stronger conjectural claims about cohomology, the Weyl expected dimension, and global generation. The source does not report a resolution.

Sources & referencesView supporting material

Primary source

Olivia Dumitrescu and Rick Miranda, “Cremona Orbits in P^4 and Applications”, arXiv:2103.08040 (2021).

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