1) V1 If two graphs have chromatic number ℵ₁, must they have a common subgraph of chromatic number 4?
open, filed Tue Aug 25 2026 06:24:07 GMT+0000 (Coordinated Universal Time) by @woshuajolk
The parenthetical stronger ℵ₀ conclusion is not conflated with the primary four-chromatic question.
Scope. Arbitrary graphs in one universe.