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arxiv: 1607.00205 · v1 · pith:JHL3P52Wnew · submitted 2016-07-01 · 🧮 math.LO

An Easton-like theorem for Zermelo-Fraenkel Set Theory without Choice

classification 🧮 math.LO
keywords kappacardinalsfunctioncardchoicecontinuuminfinitemathbb
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We show that in Zermelo-Fraenkel Set Theory without the Axiom of Choice a surjectively modified continuum function $\theta(\kappa)$ can take almost arbitrary values for all infinite cardinals. This choiceless version of Easton's Theorem is in sharp contrast to the situation in ZFC, where for singular cardinals $\kappa$, the value of $2^\kappa$ is strongly influenced by the behaviour of the continuum function below. Our construction can roughly be described as follows: In a ground model $V \models ZFC + GCH$ with a "reasonable" function $F: Card \rightarrow Card$ on the infinite cardinals, a class forcing ${\mathbb P}$ is introduced, which blows up the power sets of all cardinals according to $F$ . The eventual model $N \models ZF$ is a symmetric extension by ${\mathbb P}$ such that $\theta^N(\kappa) = F(\kappa)$ holds for all $\kappa$.

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