An acyclic edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycles. The acyclic
chromatic index of a graph is the minimum number k such that there is an acyclic edge coloring using k colors and is
denoted by a′(G). It was conjectured by Alon, Sudakov and Zaks (and much earlier by Fiamcik) that a′(G) + 2,
where = (G) denotes the maximum degree of the graph. We prove that if G is a planar graph with maximum degree
, then a′(G) + 12.