Toughness and prism-hamiltonicity of $P_4$-free graphs

M. N. Ellingham, Pouria Salehi Nowbandegani, Songling Shan

The \emph{prism} over a graph $G$ is the product $G\square K_2$, i.e., the graph obtained by taking two copies of $G$ and adding a perfect matching joining the two copies of each ver…