Mixing is hard for triangle-free reflexive graphs

Hyobeen Kim, Jae-baek Lee, Mark Siggers

In the problem $\mathrm{Mix}(H)$ one is given a graph $G$ and must decide if the Hom-graph $\mathbf{Hom}(G,H)$ is connected. We show that if $H$ is a triangle-free reflexive graph…