Feng–Horsley–Wang conjecture on disjoint base blocks in cyclic BIBDs

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Let kk and λ\lambda be fixed positive integers with k⩾λ+1k\geqslant \lambda+1. Let (X,B)(X,\mathcal B) be a cyclic (v,k,λ)(v,k,\lambda)-BIBD with v⩾v0v\geqslant v_0, where v0v_0 is an integer depending on kk and λ\lambda. Partition its blocks into orbits under the cyclic automorphism, and call a fixed block from each orbit a base block. Feng–Horsley–Wang conjecture. It is always possible to choose one block from each block orbit so that the chosen blocks are pairwise disjoint. The source records a theorem resolving the assertion when k⩾2λ+1k\geqslant 2\lambda+1, while the boundary range λ+1⩽k⩽2λ\lambda+1\leqslant k\leqslant 2\lambda is not resolved there.

References

Primary source

Xinyue Ming, Tao Feng and Menglong Zhang, “The asymptotic existence of BIBDs having a nesting”, arXiv:2405.13328 (2024).

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