Abstract:
An oriented $k$-coloring of an oriented graph $H$ is defined to be an oriented homomorphism of $H$ into a $k$-vertex tournament. It is proved that every orientation of a graph with girth at least 5 and maximum average degree over all subgraphs less than 12/5 has an oriented 5-coloring. As a consequence, each orientation of a plane or projective plane graph with girth at least 12 has an oriented 5-coloring.