Volume 17, No 2, 2010, P. 20-3888
O. V. Borodin
Acyclic 4-colorability of planar graphs without 4- and 5-cycles
Every planar graph is known to be acyclically 5-colorable (Borodin, 1976). Some sufficient conditions are also obtained for a planar graph to be acyclically 4- and 3-colorable. In particular, the acyclic 4-colorability was proved for the following planar graphs: without 3-, and 4-cycles (Borodin, Kostochka, Woodall, 1999), without 4-, 5- and 6-cycles, without 4-, 5- and 7-cycles, and with neither 4- or 5-cycles nor intersecting 3-cycles (Montassier, Raspaud and Wang, 2006), and also without cycles of length 4, 5 and 8 (Chen, Raspaud, 2009). In this paper it is proved that each planar graph without 4-cycles and 5-cycles is acyclically 4-colorable.
Keywords: planar graphs, acyclic coloring, forbidden cycles.
Borodin Oleg Veniaminovich 1,2
1. S. L. Sobolev Institute of Mathematics, SB RAS,
4 Acad. Koptyug Ave., 630090 Novosibirsk, Russia
Novosibirsk State University,
2 Pirogov St., 630090 Novosibirsk, Russia