Gallego–Purnaprajna conjecture on very ampleness of twice a polarization

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Let XX be a smooth Calabi-Yau threefold and LL a globally generated, ample line bundle. For a surface S∈∣L∣S\in |L|, write ∣L∣S∣|L\mathbin{\vert}_S| for the restriction of the linear system to SS; a curve C∈∣L∣S∣C\in |L\mathbin{\vert}_S| is nonhyperelliptic if it is smooth and nonhyperelliptic. Gallego–Purnaprajna conjecture. The line bundle 2L2L is very ample and the morphism it defines embeds XX as a projectively normal variety if and only if there is a smooth nonhyperelliptic curve C∈∣L∣S∣C\in |L\mathbin{\vert}_S| for some S∈∣L∣S\in |L|. This conjecture proposes a criterion for very ampleness and projective normality on Calabi-Yau threefolds; the supplied source does not indicate whether it has been resolved.

References

Primary source

Andreas Leopold Knutsen, “On the birationality of the adjunction mapping of projective varieties”, arXiv:1109.2439 (2011).

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