Acyclic edge coloring of planar graphs with Δ colors

An acyclic edge coloring of a graph is a proper edge coloring without bichromatic cycles. In 1978, it was conjectured that ∆(G) + 2 colors suffice for an acyclic edge coloring of every graph G [6]. The conjecture has been verified for several classes of graphs, however, the best known upper bound for as special class as planar graphs are, is ∆+12 [2]. In this paper, we study simple planar graphs which need only ∆(G) colors for an acyclic edge coloring. We show that a planar graph with girth g and maximum degree ∆ admits such acyclic edge coloring if g ≥ 12, or g ≥ 8 and ∆ ≥ 4, or g ≥ 7 and ∆ ≥ 5, or g ≥ 6 and ∆ ≥ 6, or g ≥ 5 and ∆ ≥ 10. Our results improve some previously known bounds.