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| visits | member for | 1 year, 6 months |
| seen | 17 hours ago | |
| stats | profile views | 37 |
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May 12 |
comment |
Why does every countable limit ordinal have cofinality $\omega$? By definition, a map from the least ordinal. |
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May 12 |
comment |
Why does every countable limit ordinal have cofinality $\omega$? Cofinality is always a regular cardinal. |
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May 7 |
comment |
Powers of infinite cardinals in the generic extension nope, but it doesn't really matter as we count all options (worst case is if it is 1-1). |
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May 7 |
awarded | Commentator |
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May 7 |
comment |
Linearly ordered sets “somewhat similar” to $\mathbb{Q}$ @JDH - in the definition of $\mathcal{Q}_A$, shouldn't we use $\cap$? also, how does it select just one element from $(0,\alpha)$? |
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May 6 |
comment |
Powers of infinite cardinals in the generic extension I have edited my answer. Hopefully now it works. |
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May 6 |
revised |
Powers of infinite cardinals in the generic extension added 25 characters in body |
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May 4 |
answered | Powers of infinite cardinals in the generic extension |
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May 4 |
comment |
Powers of infinite cardinals in the generic extension a small typo - it should be $\kappa \le 2^\omega$ in the last claim. |
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May 1 |
comment |
How badly can GCH fail? As mentioned below, for regular cardinals ZFC cannot put a limit. Regarding singular cardinals Shelah's PCF theory gives a definite bound. |
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Apr 13 |
comment |
A question on non-standard ordinals in $\alpha-$recursion This is lemma II 7.1 in K. Devlin "Constructibility". |
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Mar 23 |
comment |
A question on a set theoretic theorem Brian, your example refers to successor cardinals, but for limit cardinals it might hold, e.g. a weakly compact cardinal. |
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Mar 12 |
comment |
Subset of a P-ideal need not be a P-ideal If you allow higher cardinals, then a weakly compact cardinal has this property. |
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Mar 12 |
comment |
A question on almost disjoint collection For a regular cardinal $\kappa$, by a result of Ulam, it is a disjoint union of $\kappa$ stationary sets. For singular cardinals, use the same argument but on the cofinality $\kappa$. |
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Feb 27 |
comment |
structure in context of ultraproduct Small typo - in your definition of $F_U$ you should change to "for almost all i". |
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Jan 21 |
awarded | Supporter |
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Dec 31 |
answered | Ordinals definable over $L_\kappa$ |
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Dec 25 |
answered | Question about passage in Halbeisen's book |
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Oct 29 |
answered | What are some good intuitions for understanding Souslin's operation $\mathcal{A}$? |
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Sep 1 |
answered | Why is the Continuum Hypothesis (not) true? |
