Acyclic 3-choosability of planar graphs without cycles of length from 4 to 12

摘要

Every planar graph is known to be acyclically 7-choosable and is conjectured to be acyclically 5-choosable (O. V. Borodin et al., 2002). This conjecture if proved would imply both Borodin's acyclic 5-color theorem (1979) and Thomassen's 5-choosability theorem (1994). However, as yet it has been verified only for several restricted classes of graphs. Some sufficient conditions are also obtained for a planar graph to be acyclically 4- and 3-colorable. In particular, a planar graph of girth at least 7 is acyclically 3-colorable (O. V. Borodin, A. V. Kostochka and D. R. Woodall, 1999) and acyclically 3-choosable (O. V. Borodin et. al, 2009). A natural measure of sparseness, introduced by Erdo{double acute}s and Steinberg, is the absence of k-cycles, where 4 ≤ k ≤ S. Here, we prove that every planar graph without cycles of length from 4 to 12 is acyclically 3-choosable.