Uniquely D-colourable digraphs with large girth

Ararat Harutyunyan, P. Mark Kayll, Bojan Mohar +1

Let C and D be digraphs. A mapping $f:V(D)\to V(C)$ is a C-colouring if for every arc $uv$ of D, either $f(u)f(v)$ is an arc of C or $f(u)=f(v)$, and the preimage of every vertex o…