Baranyai–Katona wreath conjecture

Let knk\leq n be positive integers. Write Zn\mathbb{Z}_{n} for the integers modulo nn, and let Zn(k)\mathbb{Z}_{n}^{(k)} be the set of kk-element subsets of Zn\mathbb{Z}_{n}. A wreath is a set of the form Fπ\mathcal{F}_{\pi} obtained from a permutation π\pi of Zn\mathbb{Z}_{n} by taking the cyclically indexed blocks of kk consecutive values, as defined in the paper.

The wreath conjecture. For any positive integers knk\leq n, there is a decomposition of Zn(k)\mathbb{Z}_{n}^{(k)} into disjoint wreaths.

This conjecture generalizes Baranyai's factorization theorem for complete uniform hypergraphs. It was posed by Baranyai and reformulated in terms of wreaths by Katona; the source does not state a resolution.

Sources & referencesView supporting material

Primary source

Jan Petr and Pavel Turek, “Intervals in Dyck paths and the wreath conjecture”, arXiv:2501.07277 (2025).

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