There exist oriented planar graphs with oriented chromatic number at least sixteen
Résumé
We prove that there exist oriented planar graphs with oriented chromatic number at least 16. Using a result of Raspaud and Sopena [Good and semi-strong colorings of oriented planar graphs, Inf. Processing Letters 51, 171-174, 1994], this gives that the oriented chromatic number of the family of oriented planar graphs lies between 16 and 80.