DeBiasio's conjecture on the minimum total degree for powers of Hamilton cycles

From papers

Let DD be a digraph, and let δ(D)\delta(D) denote its minimum total degree, namely the minimum number of arcs incident with a vertex. For kNk\in\mathbb{N} and sufficiently large nNn\in\mathbb{N}, write

n=(k+3)q+r,n=(k+3)q+r,

where qq is a nonnegative integer and 0rk+20\leq r\leq k+2. The kkth power of a Hamilton cycle is obtained by including the directed arcs corresponding to consecutive forward distances at most kk along the cycle.

DeBiasio's conjecture. Every nn-vertex digraph DD satisfying

δ(D){2(11k+3)n3,if r=k+2,2(11k+3)n2,if r{k,k+1},2(11k+3)n1,otherwise,\delta(D)\geq \begin{cases} 2\left\lceil\left(1-\frac{1}{k+3}\right)n\right\rceil-3, & \text{if }r=k+2,\\ 2\left\lceil\left(1-\frac{1}{k+3}\right)n\right\rceil-2, & \text{if }r\in\{k,k+1\},\\ 2\left\lceil\left(1-\frac{1}{k+3}\right)n\right\rceil-1, & \text{otherwise}, \end{cases}

contains the kkth power of a Hamilton cycle.

The conjecture proposes the minimum total-degree threshold for powers of Hamilton cycles in digraphs. The source presents it as a conjecture but gives no resolution evidence, so its status is left open.

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Sources & referencesView supporting material

Primary source

Zhilan Wang, Shuo Wei and Jin Yan, “The exact total degree threshold for the square of a Hamilton cycle in digraphs”, arXiv:2607.13831 (2026).

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