3 papers
math.CO2026
On nontrivial cross-2-intersecting families
Jingjun Bao, Lijun Ji, Liying Yu
Two families \(\mathcal{A}\subseteq\binom{[n]}{k}\) and \(\mathcal{B}\subseteq\binom{[n]}{\ell}\) are said to be nontrivial cross-\(t\)-intersecting if \(|A \cap B| \geq t\) for al…
math.CO2025
The maximum product of sizes of cross-\(t\)-intersecting families
Jingjun Bao, Lijun Ji
Two families of sets \(\mathcal{A}\) and \(\mathcal{B}\) are called \emph{cross-\(t\)-intersecting} if \(|A \cap B| \geq t\) for all \(A \in \mathcal{A}\) and \(B \in \mathcal{B}\)…
math.CO2025
New Necessary Conditions for Existence of Strong External Difference Families
Jingjun Bao, Lijun Ji
Strong external difference families (SEDFs) were introduced by Paterson and Stinson as a more restrictive version of external difference families. SEDFs can be used to produce opti…