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15 votes
Accepted

Does stationary reflection imply Mahloness?

Not necessarily. Here's a counterexample, but I'm sure it is a ridiculous overkill in consistency strength: Suppose $\kappa$ is the least inaccessible limit of supercompact cardinals. Then $\kappa$ …
Monroe Eskew's user avatar
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14 votes

Why believe in the existence of large cardinals rather than just their consistency?

I think it can be reasonably argued that the large cardinal notions follow a common conceptual pattern, even a semi-formal template. Once we understood the characterization of measurable cardinals in …
Monroe Eskew's user avatar
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12 votes
Accepted

What is the evidence for and against the HOD conjecture?

I believe it is fair to say that the HOD Conjecture has been refuted. The HOD Conjecture is the statement that the theory ZFC + "There is an extendible cardinal" proves that there is a proper class of …
Monroe Eskew's user avatar
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11 votes
Accepted

A question regarding the relation between Freiling's Axiom of Symmetry and real-valued measu...

Real-valued measurable cardinals (RVM) are equiconsistent with 2-valued measurable cardinals. I believe this is due to Solovay and Kunen. (Solovay for the forcing direction, Kunen for the inner mode …
Monroe Eskew's user avatar
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9 votes
Accepted

Why isn't there more interest in "large powerset axioms"?

I suppose there is some interest in propositions implying large powerset. For example, a classical question at the infancy of set theory and real analysis was whether there is a probability measure on …
Monroe Eskew's user avatar
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7 votes

capturing small sets in small factors

We now have a full answer. The capturing property is equivalent to weak compactness. Yair already covered the non-inaccessible case. Now we show that this property implies the tree property at $\ka …
Monroe Eskew's user avatar
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7 votes
Accepted

"Potentially club" filters on $\omega_2$

First, your notation is nonstandard; when we write $\mathrm{Col}(\kappa,\lambda)$, this typically means the set of partial functions $p : \kappa \to \lambda$ of size $<\kappa$, i.e. reverse of yours. …
Monroe Eskew's user avatar
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7 votes

Can we have a $\kappa$-Suslin tree where $\kappa$ is above a measurable cardinal?

To complement Joel's answer and tie into the issue of $L$, consider a model $L[U]$, where $U$ is a normal measure on a cardinal $\kappa$. It is well-known that $L[U]$ satisfies GCH and $\diamondsuit_ …
Monroe Eskew's user avatar
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6 votes

Reference for proof that consistency of $\omega_1$-Erdos cardinal implies Con(Chang's Conjec...

A sketch of Silver's original argument appears in section 19 here: http://math.bu.edu/people/aki/e.pdf
Monroe Eskew's user avatar
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6 votes

PFA: A New Godel's Program & A New Large Cardinal Ladder (Updated)

If we start with an indestructibly supercompact cardinal $\kappa$, then we can do Easton forcing to get any reasonable continuum function on the regular cardinals $\geq \kappa$ and retain the supercom …
Monroe Eskew's user avatar
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6 votes
Accepted

Large cardinals and measurability in $L(A)$

For each $\alpha<\omega_1$, choose a real $r_\alpha$ that codes the ordertype $\alpha$. This sequence $\langle r_\alpha : \alpha < \omega_1 \rangle$ then codes a sequence of surjections from $\omega$ …
Monroe Eskew's user avatar
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6 votes

What is known about the least cardinal where $\kappa$ fails to be supercompact?

I'm not sure if this gets to the heart of the question, but here are some observations. For a successor ordinal $\alpha$, let $\kappa_\alpha$ be the least $\kappa>\alpha$ which is $\kappa^{+\alpha}$-s …
Monroe Eskew's user avatar
  • 18.6k
6 votes

Collapsing the cardinals between two singular cardinals

For question 2, some large cardinals imply the existence of such a forcing. Suppose $\kappa$ is 2-huge, with $j : V \to M$ an elementary embedding, $\lambda = j(\kappa)$, $\theta = j(\lambda)$, and $ …
Monroe Eskew's user avatar
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6 votes
Accepted

Forcing $\neg\square_{\omega_1}$ from a Mahlo cardinal, reference

I'll give the proof, which was told to me by Martin Zeman. Let $G \subseteq \mathrm{Col}(\omega_1,{<}\kappa)$ be generic, where $\kappa$ is Mahlo. Suppose towards contradiction that $\square_{\omega_ …
Monroe Eskew's user avatar
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5 votes
Accepted

Definition of ineffability behind reflection principles in set theory

Referring to proper classes by means of constants clearly doesn’t use the “internal properties” of the universe of sets. You’re literally reaching outside the universe and adding an artificial means …
Monroe Eskew's user avatar
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