Ordinary and spectral extremal problems on vertex disjoint copies of even fans

Yiting Cai, Bo Zhou

Let $\mathrm{ex}(n,F)$ and $\mathrm{spex}(n,F)$ be the maximum size and spectral radius among all $F$-free graphs with fixed order $n$, respectively. A fan is a graph $P_1\vee P_…