The divisible-set union conjecture

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Let rr be a positive integer. A set of points over F2\mathbb{F}_2 is 2r2^r-divisible if every hyperplane meets it in a number of points congruent to its size modulo 2r2^r. An (r+1)(r+1)-space is a projective subspace of dimension r+1r+1, and [r+1]2=(2r+1−1)/(2−1)[r+1]_2=(2^{r+1}-1)/(2-1) denotes its number of points.

Divisible-set union conjecture. There exists a function f ⁣:N→Nf\colon \mathbb{N}\to\mathbb{N} such that every 2r2^r-divisible set of f(r)⋅[r+1]2f(r)\cdot [r+1]_2 points over F2\mathbb{F}_2 is the disjoint union of f(r)f(r) (r+1)(r+1)-spaces and

lim⁡r→∞f(r)=∞.\lim_{r\to\infty} f(r)=\infty.

This conjecture proposes arbitrarily large values of rr for which a sufficiently structured divisible set must decompose into disjoint spaces. The surrounding discussion gives related small-parameter results and computational evidence, but no resolution of this assertion is supplied.

References

Primary source

Sascha Kurz, “Divisible Codes”, arXiv:2112.11763 (2025).

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