Pehova–Petrova threshold conjecture

Establish that the loose-tree embeddable threshold equals the perfect-matching threshold, namely, prove that \(\delta_{k,\ell}^{T}=\delta_{k,\ell}^{PM}\) for every pair of integers \(1\le \ell<k\).

Background

The paper defines δk,T\delta_{k,\ell}^{T} as the asymptotic relative minimum \ell-degree threshold forcing a kk-uniform hypergraph to contain every spanning kk-loose tree of bounded maximum vertex degree. It defines δk,PM\delta_{k,\ell}^{PM} as the corresponding threshold forcing a perfect matching.

Pehova and Petrova conjectured that these thresholds coincide for all 1<k1\le \ell<k. The paper verifies the conjecture for (k,)=(k,k1)(k,\ell)=(k,k-1), (3,1)(3,1), and, through its main theorem, for all =k2\ell=k-2 with k4k\ge4; the general case remains unresolved.

References

Pehova and Petrova further conjectured that $\delta_{k,\ell}{T} = \delta_{k,\ell}{PM}$ in general.

\begin{conjecture}[Pehova and Petrova]\label{Conjecture1} For all $1 \le \ell < k$, $\delta_{k,\ell}{T} = \delta_{k,\ell}{PM}$. \end{conjecture}

Embedding loose trees in $k$-uniform hypergraphs  (2502.04783 - Chen et al., 7 Feb 2025) in Conjecture 1, Section 1 (Introduction)