Two forbidden induced subgraphs and well-quasi-ordering
نویسندگان
چکیده
منابع مشابه
Subgraphs and well-quasi-ordering
Let % be a class of graphs and let i be the subgraph or the induced subgraph relation. We call % an idea/ (with respect to I) if G I G' E % implies that G E %. In this paper, we study the ideals that are well-quasiordered by I. The following are our main results. If 5 is the subgraph relation, we characterize the well-quasi-ordered ideals in terms of excluding subgraphs. If I is the induced sub...
متن کاملWell-quasi-ordering Infinite Graphs with Forbidden Finite Planar Minor
We prove that given any sequence G\, Gi,... of graphs, where G\ is finite planar and all other G, are possibly infinite, there are indices ;', j such that i < j and G¡ is isomorphic to a minor of Gj . This generalizes results of Robertson and Seymour to infinite graphs. The restriction on G\ cannot be omitted by our earlier result. The proof is complex and makes use of an excluded minor theorem...
متن کاملInduced minors and well-quasi-ordering
A graph H is an induced minor of a graph G if it can be obtained from an induced subgraph of G by contracting edges. Otherwise, G is said to be H-induced minor-free. Robin Thomas showed that K4-induced minor-free graphs are well-quasi-ordered by induced minors [Graphs without K4 and well-quasi-ordering, Journal of Combinatorial Theory, Series B, 38(3):240 – 247, 1985]. We provide a dichotomy th...
متن کاملLetter graphs and well-quasi-order by induced subgraphs
Given a word w over a 1nite alphabet and a set of ordered pairs of letters which de1ne adjacencies, we construct a graph which we call the letter graph of w. The lettericity of a graph G is the least size of the alphabet permitting to obtain G as a letter graph. The set of 2-letter graphs consists of threshold graphs, unbounded-interval graphs, and their complements. We determine the lettericit...
متن کاملLetter graphs and well-quasi-order by induced subgraphs
Given a word w over a nite alphabet and a set of ordered pairs of letters which de ne adjacencies we construct a graph which we call the letter graph of w The lettericity of a graph G is the least size of alphabet permitting to obtain G as a letter graph The set of letter graphs consists of threshold graphs unbounded interval graphs and their complements We determine the lettericity of cycles a...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 2011
ISSN: 0012-365X
DOI: 10.1016/j.disc.2011.04.023