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Questions about the continuum hypothesis, or where the continuum hypothesis or its negation plays a role. This tag is also suitable, by extension, to refer to the generalized continuum hypothesis and related issues.

11 votes
2 answers
2k views

Can GCH fail everywhere every way?

The following question is about if it is compatible to add to $\sf ZF$ an axiom asserting the existence of a countable transitive model of $\sf ZF$ such that for every strictly increasing function $f$ …
Zuhair Al-Johar's user avatar
4 votes
1 answer
527 views

How to settle the Generalized Continuum Hypothesis when there are urelements?

Work in $\sf ZFCA$ and permutation models has preceded forcing by several decades. Was it used to settle the question of the Generalized Continuum Hypothesis $\sf GCH$ when urelements are admitted? I …
Zuhair Al-Johar's user avatar
2 votes
1 answer
178 views

If GCH is breached the same way before a singular of uncountable cofinality, would that brea...

By 1 step breach of the GCH I mean the following: $$ 2^{\aleph_{\alpha}} = \aleph_{\alpha+2}$$ Now, it is known that there are more constrains on the cardinality of power sets at singlular cardinals t …
Zuhair Al-Johar's user avatar
2 votes
0 answers
159 views

What is the consistency strength of the following pattern of failure of the continuum hypoth...

What is the least theory in which the following sentence is proved? $ \exists M: M\text { is CTM(ZFC+ GCH)} \land \forall \kappa \in Card^M (\kappa > 1 \implies \\\exists N: N \text { is CTM(ZFC) } …
Zuhair Al-Johar's user avatar
1 vote
1 answer
148 views

Is existence of a cardinal that witness non-failure of GCH everywhere everyway, a theorem of...

In an earlier positing to $\mathcal MO$, it appears that the answer to if the $\sf GCH$ can fail everywhere in every way is to the negative, this is the case in $\sf ZFC$, however it also appears that …
Zuhair Al-Johar's user avatar
1 vote
0 answers
182 views

Can GCH fail everywhere in every finite way?

Since the $\sf GCH$ cannot fail everywhere everyway (see here), the question here is if it can fail everywhere in every finite manner, that if we have a strictly increasing function $f$ on the ordinal …
Zuhair Al-Johar's user avatar
1 vote
1 answer
181 views

What's the consistency status/strength of this limitation principle?

$\DeclareMathOperator\iCard{iCard}$In a prior posting If we limit matters what ZFC can prove, would that be consistent? to MO, I tried to capture the informal principle of whatever ZFC proves, it is, …
Zuhair Al-Johar's user avatar
0 votes
0 answers
136 views

What's the consistency strength of resemblance + global failure of the continuum hypothesis?

Let $T$ be a theory formalized in first order logic with equality and membership and the additional primitive constant symbol $W$, with the following axioms: Extensionality: $\forall z (z \in x \left …
Zuhair Al-Johar's user avatar
-2 votes
1 answer
173 views

Which extension of ZFC proves that ZFC can only prove CH satisfied by the first two sets?

Which extension of $\sf ZFC$ prove that $$ {\sf ZFC} \not \vdash \exists x \, ( \operatorname {CH}(x) \land x \neq \emptyset \land x \neq 1)$$ Where $\operatorname {CH}(x) \iff \neg \exists \kappa \, …
Zuhair Al-Johar's user avatar