Exact spectral threshold conjecture for perfect matchings in balanced 3-partite 3-graphs

Let HH be a 33-partite 33-graph with three vertex classes of size nn. For each vertex vv, let NH(v)N_H(v) be its link graph and let ρ(NH(v))\rho(N_H(v)) denote the spectral radius of its adjacency matrix. Define

τ(n)={n(n1)2,if n is odd,12n2n+2+n46n3+9n2+12n12,if n is even.\tau(n)=\begin{cases} \displaystyle\sqrt{\frac{n(n-1)}{2}},&\text{if $n$ is odd},\\[12pt] \displaystyle\frac12\sqrt{n^2-n+2+\sqrt{n^4-6n^3+9n^2+12n-12}},&\text{if $n$ is even}. \end{cases}

Exact spectral threshold conjecture. If

ρ(NH(v))>τ(n)\rho(N_H(v))>\tau(n)

for every vertex vV(H)v\in V(H), then HH contains a perfect matching.

The conjecture proposes the exact finite-nn strengthening of the paper's asymptotic spectral theorem. The displayed odd and even constructions show that the threshold is asymptotically tight, but the supplied source does not state that this exact form has been proved or refuted.

Sources & referencesView supporting material

Primary source

Hongliang Lu and Feihong Yuan, “A spectral condition for perfect matchings in 3-partite 3-graphs”, arXiv:2606.15771 (2026).

Additional references

4 papers in this index state this conjecture (2011–2026). The statement above is taken from the most recent of them; the others are arXiv:2407.11163, arXiv:2309.05182, arXiv:1112.1360.

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.