User over - MathOverflowmost recent 30 from http://mathoverflow.net2013-05-24T12:33:56Zhttp://mathoverflow.net/feeds/user/15147http://www.creativecommons.org/licenses/by-nc/2.5/rdfhttp://mathoverflow.net/questions/65774/definition-of-a-limit-of-a-typeDefinition of a limit of a typeover2011-05-23T17:42:16Z2011-05-23T17:42:16Z
<p>I apologize if this is not the right forum to ask such a basic question...
In model theory what does that mean that a type concentrates on one point?</p>
http://mathoverflow.net/questions/46156/is-every-closed-set-of-q-the-intersection-of-some-connected-closed-set-of-r-wit/65132#65132Answer by over for Is every closed set of Q² the intersection of some connected closed set of R² with Q²over2011-05-16T12:25:31Z2011-05-16T12:25:31Z<p>There might be something wrong with this suggestion but isn't it all right to enumerate all points of F and then connect two "consecutive" points the way Guillaume described in his question (by drawing two lines with irrational slope)?</p>
http://mathoverflow.net/questions/65774/definition-of-a-limit-of-a-typeComment by overover2011-05-30T02:11:15Z2011-05-30T02:11:15ZI know that this is equivalent to a third fact that is: any M-definable curve in X is completable. ($ X \subset M^n$ with M be an o-minimal structure)
(a curve in X is a M-definable continuous embedding f: $(a,b) \stackrel{}{\rightarrow} X$ where (a,b)$\subset$M.
It is said to be completable if $\lim_{x\rightarrow a^{+}} f (x) $ and $\lim_{x\rightarrow b^{-}} f (x)$ exist.)
I've been told one can associate a definable type to such a curve. But I'm not sure of how. %aybe this would help to understand it?
http://mathoverflow.net/questions/65774/definition-of-a-limit-of-a-typeComment by overover2011-05-30T02:10:28Z2011-05-30T02:10:28ZThank you for your ansswers.
The type is supposed to be definable. I'm sorry I should have mentionned it maybe the notion of limit of a type makes sense otherwise.
I've found this definition:
M is an o-minimal structure.
A point a of $M^n$ is a limit of p a definable type if for any definable neighborhood U of a (defined with parameters), p concentrates on U.
The context is the following theorem:
let M be an o-minimal structure, $ X \subset M^n$ then the fact that X is closed and bounded, is equivalent to the fact that any definable type concentrates on one point.
http://mathoverflow.net/questions/46156/is-every-closed-set-of-q-the-intersection-of-some-connected-closed-set-of-r-wit/65132#65132Comment by overover2011-05-17T20:08:41Z2011-05-17T20:08:41Zoh yes! That's right! Thanks for your help!