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Rado's theorem is a theorem from the branch of mathematics known as Ramsey theory. It is named for the German mathematician Richard Rado. It was proved in his thesis, ''Studien zur Kombinatorik''. Let be a system of linear equations, where is a matrix with integer entries. This system is said to be ''-regular'' if, for every -coloring of the natural numbers 1, 2, 3, ..., the system has a monochromatic solution. A system is ''regular'' if it is ''r-regular'' for all ''r'' ≥ 1. Rado's theorem states that a system is regular if and only if the matrix ''A'' satisfies the ''columns condition''. Let ''ci'' denote the ''i''-th column of ''A''. The matrix ''A'' satisfies the columns condition provided that there exists a partition ''C''1, ''C''2, ..., ''C''''n'' of the column indices such that if , then # ''s''1 = 0 # for all ''i'' ≥ 2, ''si'' can be written as a rational〔Modern graph theory by Béla Bollobás. 1st ed. 1998. ISBN 978-0-387-98488-9. Page 204〕 linear combination of the ''cjs in the ''Ck'' with ''k'' < ''i''. Folkman's theorem, the statement that there exist arbitrarily large sets of integers all of whose nonempty sums are monochromatic, may be seen as a special case of Rado's theorem concerning the regularity of the system of equations : where ''T'' ranges over each nonempty subset of the set 〔.〕 ==References== 〔 Category:Theorems in discrete mathematics 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Rado's theorem (Ramsey theory)」の詳細全文を読む スポンサード リンク
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