Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


Math Forum
»
Discussions
»
sci.math.*
»
sci.math
Notice: We are no longer accepting new posts, but the forums will continue to be readable.
Topic:
Open and Shut
Replies:
10
Last Post:
Feb 4, 2013 10:50 PM




Re: Open and Shut
Posted:
Feb 3, 2013 7:52 PM


On Feb 3, 3:58 pm, Virgil <vir...@ligriv.com> wrote: > In article <Pine.NEB.4.64.1302022012270.25...@panix3.panix.com>, > William Elliot <ma...@panix.com> wrote: > > > A subset A, of an ordered set is convex when > > for all x,y in A, for all a, (x <= a <= y implies a in A). > > > I will call an interval an order convex subset of Q. > > Given an interval, what's the probablity that it's > > open, closed, both, neither? > > The only probability that is certain in Q is that the probability of > being both open and closed is zero, as Q and {} are the only nonempty > orderconvex sets in Q that are both open and closed under the order > toology, and there are infinitely many other intervals which are not > both open and closed. > > To do more one needs to make some assumptions about the probability > of a nonempty set of rationals which is (finitely) bounded above > containing its least upper bound or a nonempty set of rationals which > is (finitely) bounded below containing its greatest lower bound. > > > Given an open subset of Q, what's the probablity that it's clopen? > > Zero. ONly {} and Q are both closed and open> Given an closed subset of Q, what's the probablity that it's clopen? > > Zero. ONly {} and Q are both closed and open
Does this mean that Q is connected?



