3-CHOOSABILITY OF TRIANGLE-FREE PLANAR GRAPHS WITH CONSTRAINTS ON 4-CYCLES

被引:7
|
作者
Dvorak, Zdenek [1 ]
Lidicky, Bernard [1 ]
Skrekovski, Riste [2 ]
机构
[1] Charles Univ Prague, Fac Math & Phys, Dept Appl Math, Prague 11800, Czech Republic
[2] Univ Ljubljana, Dept Math, Ljubljana 1111, Slovenia
关键词
planar graph; triangle-free graph; coloring; list coloring; choosability; LIST COLORINGS; LEAST; 4; GIRTH; MAP;
D O I
10.1137/080743020
中图分类号
O29 [应用数学];
学科分类号
070104 ;
摘要
A graph is k-choosable if it can be colored whenever every vertex has a list of at least k available colors. We prove that if a triangle-free planar graph is not 3-choosable, then it contains a 4-cycle that intersects another 4- or 5-cycle in exactly one edge. This strengthens Thomassen's result [C. Thomassen, J. Combin. Theory Ser. B, 64 (1995), pp. 101-107] that every planar graph of girth at least 5 is 3-choosable. In addition, this implies that every triangle-free planar graph without 6- and 7-cycles is 3-choosable.
引用
收藏
页码:934 / 945
页数:12
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