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Erdős problem 70

Erdős Problem 70: Let c\mathfrak{c} be the cardinality of the continuum, let β\beta be a countable ordinal, and let 2n<ω2 \le n < \omega. Is it true that c(β,n)23\mathfrak{c} \to (\beta, n)^3_2?

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FormalConjectures/ErdosProblems/

70.lean

Retained formal statement3 of 6

**The relation at ω1\omega_1**: c(ω1,n)23\mathfrak{c} \to (\omega_1, n)^3_2 for finite n2n \ge 2, where ω1=1\omega_1 = \aleph_1 is the first uncountable ordinal.

Note that ω1\omega_1 is *not* a countable ordinal, so this is not directly an instance of the main Erdős problem (which asks for *countable* β\beta). Under CH, ω1=c.ord\omega_1 = \mathfrak{c}.\mathrm{ord}, making this a self-referential question about c.ord(c.ord,n)23\mathfrak{c}.\mathrm{ord} \to (\mathfrak{c}.\mathrm{ord}, n)^3_2.

FormalConjectures/ErdosProblems/70.leanErdos70.erdos_70.variants.omega_one1 lineExact file
True ↔ ∀ (n : ℕ), 2 ≤ nErdos70.OrdinalCardinalRamsey3 Cardinal.continuum.ord (Cardinal.aleph 1).ordn
OpenStatement only, no proof

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