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4
votes
0
answers
280
views
Reflection principles justifying $I2$ and larger cardinals
Consider the language of set theory together with the constant smybols $\langle \Omega_\alpha|\alpha\in Ord\rangle$. Let's add to $ZFC$ the axiom that for every $\alpha$,$n$ there is some $j: V_{\Omeg …
2
votes
Accepted
Limit of Mahlo cardinals
There is some problems with definitions here.
The definition you use of $\alpha+1$-Mahlo cardinals is a cardinal $\kappa$ such that $\kappa$ is the $\kappa$th $\alpha$-Mahlo cardinal.
This is not the …
2
votes
1
answer
233
views
Possible inconsistency related to embeddings $j: M\prec V$
In the paper
Vickers, J.; Welch, P. D., On elementary embeddings from an inner model to the universe, J. Symb. Log. 66, No. 3, 1090-1116 (2001). ZBL1025.03049.
it is stated to that if $Ord$ is R …
2
votes
Large cardinals and reflection properties
There is actually a type of cardinal that satisfies this, called the "stationarily superhuge" cardinals. A cardinal $\kappa$ is called stationarily superhuge if the $\{\lambda|\kappa\text{ is huge wit …
3
votes
Critical points of rank-into-rank embeddings
Theorem: If $\kappa$ is the critical point of $j\colon V_\lambda\prec V_\lambda$, then $\kappa$ is $\lambda$-weakly extendible. Furthermore, if $\kappa$ is the critical point of $j\colon V_\lambda\pre …
4
votes
Aleph 0 as a large cardinal
There is a sense in which rank-into-rank axioms could be considered generilzations of $\omega$. Woodin discussed this in his paper Suitable Extender Models $I$, given the following conjecture, which I …
4
votes
1
answer
603
views
What is the consistency strength of almost $\omega$-huge cardinals?
What is the consistency strength of a cardinal $\kappa$, such that there is some $j: V\prec M$ such that $M^{\lt j^\omega(\kappa)}\subseteq M$; in other words, for every cardinal $\lambda\lt\delta$, $ …
2
votes
"Bootstrapping" an unbounded class of inaccessible cardinals
There are three interesting types of upwards reflection. First off, reflecting upwards to an unbounded class of cardinals, or reflecting oneself upwards, or both. The other instance is when you can fi …
5
votes
How elementary can we go?
I would like to mention, on the second question, that superhuge cardinals are in fact $\Sigma_5$-reflecting, that is to say inaccessible and $V_\kappa\prec_{\Sigma_5} V$. The reason is first that ever …
2
votes
Accepted
Bernays' Reflection Principle holding in ranks?
I would like to add that, for $n>1$, the $\Pi_n-$Bernays cardinals are precisely the $\Pi_n^1-$indescribable cardinals. We can do this really simply by giving a $\Pi_2$ definition of the Axiom of limi …
2
votes
Superextendibles defined analogously to superstrong cardinals: Where are they consistency st...
These large cardinals actually already have a name. They are called $n$-huge* cardinals.
Theorem: If $\kappa$ is $n$-huge*, then $\kappa$ is $n$-huge and a limit of $n$-huge cardinals.
Proof. Let $j: …
10
votes
Accepted
Large cardinals ordered by cardinality of least instance
I added some information elsewhere, but it was to long to put in one post: http://metaordinals.azurewebsites.net/?p=261
Part 1: Your ordering is correct, but the size of the gaps are much more complex …
9
votes
0
answers
2k
views
What are the known implications of “There exists a Berkeley cardinal”?
Inspired by this question: What are the known implications of "There exists a Reinhardt cardinal" in the theory "ZF + j"?
Definitions:
$\delta$ is Berkeley iff for every $\alpha\lt\delta$ and transit …
-1
votes
$\Pi_0^1$-weakly indescribable cardinals are exactly the regulars
First off, note that being weakly $\Pi^1_0$-indescribable is actually the same as being weakly $\Sigma_1^1$-indescribable. Let $\phi(x_0...x_n,S)$ be some formula, say $\exists X(\psi(X,x_0...x_n,S))$ …
8
votes
0
answers
415
views
Choice function for elementary embedding $j: V_\lambda\prec V_\lambda$
Work in ZF. Let $\lambda$ be strongly inaccessible. Let $\kappa$ be such that for every $\alpha\lt\lambda$, there is some $j: V_\lambda\prec V_\lambda$, with critical point $\kappa$, such that $j(\kap …