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Blocking Set


A blocking set in a finite projective plane is a set of points meeting every line. It is minimal if deleting any point destroys this property. In PG(2,q) it is small when its size is less than 3(q+1)/2 (Sziklai 2026).

The linearity conjecture asserts that every small minimal blocking set consists of the F_q-projective points represented by the nonzero vectors of a subspace U subset= F_q^3 over a subfield. Write q=p^h, where p is prime, and let e be the largest exponent for which every line meets the blocking set in 1  (modp^e) points. Sziklai (2026) reports a proof of linearity over F_(p^e) when p^e=2 or p^e>=5. The general cases p^e=3 and 4 are not covered. The smallness hypothesis is essential to the stated result, and the complete argument requires further independent verification. Sziklai (2026) reports AI assistance with mathematical exploration and computations.


See also

Finite Geometry, Projective Plane

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References

Hirschfeld, J. W. P. Projective Geometries over Finite Fields, 2nd ed. Oxford, England: Clarendon Press, 1998. https://doi.org/10.1093/oso/9780198502951.001.0001.Sziklai, P. "The Linearity Conjecture." 21 Oct 2026. https://arxiv.org/abs/2610.30503.

Cite this as:

Weisstein, Eric W. "Blocking Set." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/BlockingSet.html

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