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8
votes
Accepted
Mahlo cardinal and hyper k-inaccessible cardinal
The answer is no. Mahloness is much stronger than this.
Every Mahlo cardinal $\kappa$ is a limit of such cardinals. One can see this, because there is a club of $\gamma<\kappa$ with $V_\gamma\prec V …
7
votes
Accepted
Do strong embeddings always provide all the ultrafilters that exist?
If all we want is that for every measure $U$ there is a strongness
embedding with a seed for $U$, then the answer is yes. To see
this, suppose $\kappa$ is a strong cardinal, and let $U$ be any
$\kappa …
12
votes
Accepted
A question about "local" versus "global" large cardinal axioms
I don't agree that it is difficult to formalize the local/global distinction, and indeed, I think that there is a largely agreed-upon technical meaning for these notions.
Specifically, a property is …
11
votes
Accepted
Is there a large-cardinal completeness theorem for $L$?
On the one hand, we cannot easily describe any such list of axioms, since if $\Lambda$ was computably enumerable, then by your third bullet point, the arithmetic consequences of ZFC+(V=L)+$\Lambda$ wo …
5
votes
Accepted
Covering properties of strongly compact embedding
This is a very nice question (and indeed, I remember asking myself this question when I was a graduate student).
The answer in general is that no, you do not get any extra strength from having these …
4
votes
Accepted
Elementary embeddings with the same critical point
Yes, this situation can occur. One should simply undertake the dual of the construction you had suggested with iterated ultrapowers.
Specifically, suppose that $\mu$ is a normal measure on a measura …
7
votes
Accepted
Is there a simple combinatorial characterization for when a direct limit of ultrapowers of $...
The answer is yes.
Theorem. The direct limit ultrapower you describe is
well-founded if and only if $\bigcap_n A_n\neq \emptyset$ whenever
$A_n\in U$ for all $n$.
Proof. You've already noted the con …
5
votes
Accepted
$\text{ZFGC}^{\text{−f}}+\text{BAFA}+\exists\kappa(κ \text{ is Reinhardt})$ and its implication
I'm glad to hear you're reading our paper, which can be found here: The foundation axiom and elementary self-embeddings of the universe. Click through to the arxiv for a pdf — and I note that the titl …
8
votes
Increasing and Descending Chains of Inner Models for Measurable Cardinals
I assume that by $M_{\kappa,\mu}$ you intend the ultrapower of $V$ by $\mu$.
Both of the statements are inconsistent, even in the case of only two measurable cardinals, let alone a proper class of t …
7
votes
Accepted
If $\kappa$ is weakly inaccessible, then is it the $\kappa$-th aleph fixed point
If $\kappa$ is weakly inaccessible, then it is a limit cardinal and hence $\kappa=\aleph_\lambda$
for some limit ordinal $\lambda$. Since the cofinality of $\aleph_\lambda$ is
the same as the cofinali …
8
votes
Accepted
Applications of higher-order reflection principles
I view these kinds of hypotheses as on a continuum stretching from
weak compactness up through all the levels of the indescribability
hierarchy, second order, third order and so on. This hierarchy of
…
10
votes
Accepted
The Kunen inconsistency and definable classes
My perspective on this issue is that there are a variety of ways to take the claim of the Kunen inconsistency, and we needn't pick a particular one as the only right one. Rather, we gain a fuller pers …
4
votes
A question about supercompact cardinal numbers
No, this is not possible.
If κ is supercompact, then in particular it is measurable, and there is a normal measure μ on κ that concentrates on non-measurable cardinals. If j:V to M is the correspond …
8
votes
Accepted
Strong Cardinals and Supercompact Cardinals
In general, $\lambda$-supercompactness, if consistent, does
not imply $\lambda$-strongness. One can see this by
observing that the smallest cardinal $\kappa$ that is
$\kappa^+$-supercompact is never $ …
4
votes
Accepted
Ultrapowers by normalized ultrafilters
I would answer question 1 by saying that
$M=\text{Ult}(V,U)$ if and only if $j$ is isomorphic to an
ultrapower by some normal measure. This is another way of
saying that normal measures are minimal wi …