[Math] Shortest formal statement equivalent to the continuum hypothesis

lo.logicset-theorysoft-question

What is the shortest formal statement you can write that is provably equivalent to the Continuum Hypothesis in ZFC?

Please use only variables and the following symbols: $\forall, \exists,\lor,\land,\neg,\to, \in,=$ (parentheses may be added for convenience and do not contribute to the length of the formula). For example, symbols and expressions like $\subset,\emptyset,\{\dots\},\aleph_0,\mathcal{P}(x)$ are not allowed for purposes of this problem. Please give references if equivalence of your statement with $CH$ is not immediately obvious.

Best Answer

I don't know if this is the shortest (number of symbols?) but in

D. Scott, "A Proof of the Independence of the Continuum Hypothesis", THEORY OF COMPUTING SYSTEMS, Volume 1, Number 2. Available at: http://www.springerlink.com/content/hh339022jt1m5183/

there is (at the bottom of page 1) a concise formulation of CH. The sentence actually uses the symbol $\mathbb{N}$ for the natural numbers, but you can get rid of it of course.

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