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Rationality and realizability of the WLP binary sequence b_X

Investigate whether, for a finite set of points X ⊂ P^r, the real number b_X = 0.b1 b2 b3 …—where b_d = 1 if R/A_{X,d} has the Weak Lefschetz Property and b_d = 0 otherwise—is always rational; and classify which real numbers with binary expansions arising from 0–1 sequences can be realized as b_X for some X ⊂ P^r.

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Background

The authors propose encoding the WLP behavior across all powers d by a binary sequence B_X and the associated real number b_X in [0,1]. In P2, b_X corresponds to the constant-1 sequence due to known WLP results, while in P3 more varied behaviors occur.

This question asks about eventual stability and periodicity (rationality corresponds to ultimately periodic binary expansions) and seeks a characterization of which numbers arise from geometric configurations X in projective space.

References

Question 8.9. Fix n and let X be a set of points in Pr. Construct the sequence Bx = (b1, b2, b3, ... ) as follows: ba = 1 if Ax,a has the WLP, otherwise it is 0. Also define from Bx the corresponding real number bx = 0.b1b2b3 .... Is bx a rational number? Which numbers b constructed from a sequence of 0 and 1 as above are such that b = bx for some set of points in Pr?

On the Weak Lefschetz Property for certain ideals generated by powers of linear forms (2406.09571 - Favacchio et al., 13 Jun 2024) in Section 8, Question 8.9