Difference between revisions of "User talk:Rkossak"

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-== Omitting theories of undefinable sets ==
-Suppose $M$  is  countable recursively saturated and
-$X$ is an undefinable subset of $M$. Is there a countable recursively saturated  $N$ such that $N$ is an elementary end extension of $M$,
-and if $Y \subseteq M$ is coded in $N$, then $(M,Y) \not\equiv
-(M,X)$?
-The answer if `yes' is either $(M,X)\not\models PA^*$ or ${\rm Th}(M,X)\notin {\rm SSy}(M)$.

Latest revision as of 13:12, 16 January 2013