Ellis–Keller–Lifshitz stability conjecture for intersecting families

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Let nn, kk, tt, and dd satisfy

n≥(t+1)(k−t+1),d∈N.n\geq(t+1)(k-t+1),\qquad d\in\mathbb{N}.

Let F⊆([n]k)\mathcal{F}\subseteq\binom{[n]}{k} be tt-intersecting. Ellis–Keller–Lifshitz stability conjecture. If

∣F∣≥max⁡{(t+2)(n−t−2k−t−1)−(t+1)(n−t−2k−t−2),(n−tk−t)−(n−t−dk−t)+t(n−t−dk−t−d+1)},|\mathcal{F}|\geq\max\left\{(t+2)\binom{n-t-2}{k-t-1}-(t+1)\binom{n-t-2}{k-t-2}, \binom{n-t}{k-t}-\binom{n-t-d}{k-t}+t\binom{n-t-d}{k-t-d+1}\right\},

then there exists a tt-subset XX such that

∣F∖F[X]∣≤t(n−t−dk−t−d+1).|\mathcal{F}\setminus\mathcal{F}[X]|\leq t\binom{n-t-d}{k-t-d+1}.

Here F[X]\mathcal{F}[X] denotes the subfamily of members of F\mathcal{F} containing XX. The conjecture was proposed by Ellis, Keller and Lifshitz as a strengthening of their stability theorem for tt-intersecting families. The supplied text does not state whether it has been resolved.

References

Primary source

Jie Wen and Benjian Lv, “A unified approach to cross-intersection problems with applications to Hilton–Milner type theorems and stability”, arXiv:2607.03315 (2026).

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