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Existence of (b, d)-geprofi sets in P4 in linear general position for fixed d and large b

Determine whether, for a fixed integer d ≥ 2 and sufficiently large b, there exists a (b, d)-geprofi set Z ⊂ P4 with |Z| = bd whose points are in linear general position and whose general projection to P3 is the full intersection of a curve of degree b and a surface of degree d.

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Background

The paper introduces (b, d)-geprofi sets in P4 and proves broad existence results, including nontrivial examples and many instances in linear general position (LGP), especially for fixed b and large d (see Theorem C / Corollary 6.7).

However, the authors explicitly note that the complementary direction—fixing d and letting b grow—remains unknown, and they pose it as an open question focused on LGP configurations. This question probes the asymptotic existence of bd-point configurations in LGP whose general projection to P3 becomes a full intersection of a degree-b curve and a degree-d surface.

References

We remark that we do not know what happens in the other direction. Indeed, our work suggests the following two interesting open questions. Question 1.4. (1) For fixed d and b >> 0, does there exist a (b, d)-geprofi set in LGP? (See Question 6.13 for more in this direction.)

Finite sets of points in $\mathbb{P}^4$ with special projection properties (2407.01744 - Chiantini et al., 1 Jul 2024) in Question 1.4 (1), Section 1