The node-count conjecture for factoriality of nodal threefolds
The node-count conjecture for factoriality of nodal threefolds
Let be the nodal double-cover threefold described above, and let be a nodal hypersurface of degree as described above. The notation and denotes their singular loci, and a threefold is -factorial if every Weil divisor has a positive multiple that is Cartier.
Node-count conjecture. The inequalities
and
respectively imply the -factoriality of the threefolds and .
The claim proposes that the examples immediately preceding it are asymptotically sharp: at the displayed node counts, the corresponding threefolds can fail to be -factorial, while strict improvement of those bounds should force -factoriality. The supplied text gives no resolution of this expectation.
Sources & referencesView supporting material
Primary source
Ivan Cheltsov, “On factoriality of nodal threefolds”, arXiv:math/0405221 (2004).
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