The size of a minimum five-chromatic K4-free graph
نویسندگان
چکیده
منابع مشابه
Making a K4-free graph bipartite
We show that every K4-free graph G with n vertices can be made bipartite by deleting at most n/9 edges. Moreover, the only extremal graph which requires deletion of that many edges is a complete 3-partite graph with parts of size n/3. This proves an old conjecture of P. Erdős.
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Let G be a K4-minor-free graph with maximum degree . It is known that if ∈ {2, 3} then G2 is ( + 2)-degenerate, so that (G2) ch(G2) + 3. It is also known that if 4 then G2 is ( 3 2 + 1)-degenerate and (G2) 3 2 + 1. It is proved here that if 4 then G2 is 3 2 -degenerate and ch(G2) 3 2 + 1. These results are sharp. © 2007 Elsevier B.V. All rights reserved.
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 1993
ISSN: 0012-365X
DOI: 10.1016/0012-365x(93)90309-h