Exact results and the structure of extremal families for the Duke--Erdős forbidden sunflower problem

Andrey Kupavskii, Fedor Noskov

In 1977, Duke and Erdős asked the following general question: What is the largest size of a family $\mathtt{F}\subset \left(\genfrac{}{}{0ex}{}{[n]}{k}\right)$ that does not contain a sunflower with $s$ pe…