6 problems
Grünbaum's conjecture. Every planar graph admits an acyclic coloring with colors.
Neumann–Lara's conjecture. Every planar digraph of digirth at least can be vertex-partitioned into two acyclic sets.
McDiarmid–Mohar conjecture. Every oriented graph satisfies
Erdős's conjecture. The acyclic chromatic number satisfies
Erdős's conjecture. The acyclic chromatic number satisfies
Let be a maximal planar graph. A vertex of is called odd if it has odd degree. Odd-vertex obstruction conjecture. If contains no odd vertices, then does not admit a…