Pasotti–Pellegrini's odd-order near-factor conjecture

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Let KvK_v be the complete graph on vv vertices, where v=2n+1v=2n+1 is odd, and define edge-length by

ℓ(x,y)=min⁡(∣x−y∣,v−∣x−y∣).\ell(x,y)=\min(|x-y|,v-|x-y|).

A near 11-factor FF is a spanning subgraph of KvK_v with one isolated vertex and a matching on the remaining vertices. Let LL be a list of nn positive integers not exceeding nn, and call it admissible when, for every divisor dd of vv, the number of multiples of dd appearing in LL is at most v−d2\frac{v-d}{2}.

Pasotti–Pellegrini conjecture. There exists a near 11-factor FF of KvK_v with ℓ(F)=L\ell(F)=L if and only if LL is admissible.

The source reports partial results but states that this conjecture remains widely open. It generalizes Meszka's problem from prime order to arbitrary odd order.

References

Primary source

M. A. Ollis, Anita Pasotti, Marco A. Pellegrini and John R. Schmitt, “New methods to attack the Buratti-Horak-Rosa conjecture”, arXiv:1912.07377 (2020).

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