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Problem #638: Let $S$ be a family of finite graphs such that for every...

Let $S$ be a family of finite graphs such that for every $n$ there is some $G_n\in S$ such that if the edges of $G_n$ are coloured with $n$ colours...

Problem Statement

Let $S$ be a family of finite graphs such that for every $n$ there is some $G_n\in S$ such that if the edges of $G_n$ are coloured with $n$ colours then there is a monochromatic triangle.

Is it true that for every infinite cardinal $\aleph$ there is a graph $G$ of which every finite subgraph is in $S$ and if the edges of $G$ are coloured with $\aleph$ many colours then there is a monochromatic triangle.
Categories: Graph Theory Ramsey Theory

Progress

Erdős writes 'if the answer is affirmative many extensions and generalisations will be possible'.

Source: erdosproblems.com/638 | Last verified: January 15, 2026

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