Difference between revisions of "Superstrong"
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A cardinal $\kappa$ is ''n-superstrong'' if there is an elementary embedding $j:V\to M$ of the universe $V$ into a transitive class $M$, with critical point $\kappa$, such that $V_{j^n(\kappa)}\subset M$. | A cardinal $\kappa$ is ''n-superstrong'' if there is an elementary embedding $j:V\to M$ of the universe $V$ into a transitive class $M$, with critical point $\kappa$, such that $V_{j^n(\kappa)}\subset M$. | ||
| − | $\kappa$ is ''superstrong'' if it is 1-superstrong. 0-superstrongness is equivalent to $\kappa$-[[strong | + | $\kappa$ is ''superstrong'' if it is 1-superstrong. 0-superstrongness is equivalent to $\kappa$-[[strong | strongness]]. |
Revision as of 07:00, 10 September 2017
A cardinal $\kappa$ is n-superstrong if there is an elementary embedding $j:V\to M$ of the universe $V$ into a transitive class $M$, with critical point $\kappa$, such that $V_{j^n(\kappa)}\subset M$.
$\kappa$ is superstrong if it is 1-superstrong. 0-superstrongness is equivalent to $\kappa$- strongness.
Relation to other large cardinal notions
Every superstrong cardinal is a Shelah cardinal.
If $\kappa$ is superstrong as witnessed by $j:V \to M$, then $\kappa$ is a strong cardinal in the model $M_{j(\kappa)}$. However, superstrong cardinals need not be strong in $V$. In fact, the least superstrong cardinal is less than the least strong cardinal, because superstrongness is a $\Sigma_2$ property (as can be seen using its characterization in terms of extenders) whereas every strong cardinal is $\Sigma_2$-reflecting.
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