On Tuesday, June 26, 2018 at 2:39:44 PM UTC-4,
transf...@gmail.com wrote:
> Am Dienstag, 26. Juni 2018 18:31:46 UTC+2 schrieb
exflaso....@gmail.com:
> > On Tuesday, June 26, 2018 at 12:14:32 PM UTC-4,
transf...@gmail.com wrote:
> > > Am Dienstag, 26. Juni 2018 16:49:01 UTC+2 schrieb
exflaso....@gmail.com:
> > > > On Tuesday, June 26, 2018 at 6:49:16 AM UTC-4, WM wrote:
> > > > > But the Binary Tree distinguishes at most aleph_0 paths.
> > > >
> > > > If so, then you should be able to put them into a list.
> > >
> > > Chuckle. The list argument is purest nonsense.
> >
> > It's the surest way to prove that a set is countable.
>
> It has been applied to show that the set of nodes is countable.
> The set of paths however is restricted by the nodes to countable.
The set of finite paths, yes. Indeed, every node defines exactly one finite path: the path it takes to get to it from the root node. So any list of the nodes is automatically a list of the finite paths.
But the infinite paths cannot be defined by reference to any specific nodes. They must be defined in other ways, such as with infinite sequences of nodes: R000̄, R100̄, R010̄, R110̄, etc.
> > If you aren't able to list it, then you aren't able to count it, and if you aren't able to count it, it isn't countable.
>
> It is in bijection with a subset of a countable set. That is enough.
If you actually had such a bijection, you could easily provide a list, just by bijecting with the natural numbers and using their inherent ordering.
So, provide your list. If you have a bijection with the natural numbers, you should be able to tell me which path is 1st, the 10th, the 100th, and in general, the Nth.
> > > > Loose, vague intuitions about infinity are notoriously worthless. You need a rigorous proof, not hand-waving.
> > >
> > > On priciple I do not prove 1 + 1 = 2 and related simple stuff. But since you seem to be interested I will outline the basics sufficient to let everyone with IQ > 80 understand.
> > >
> > > The finite Binary Tree with n levels has 2^n finite paths.
> >
> > I didn't ask about the finite paths.
>
> But they will help you to understand the infinite paths.
I "understand" just fine. I'm not interested in loose, vague intuitions. I only want a rigorous proof, and as a natural consequence of the definition of "countable", in order for a set to be countable, it must be listable.
If it is impossible to provide such a list, then the set is not countable.
Maybe you want "countable" to mean something else, but if so, you should use a different term, because that one is already taken.
> > Your "path bunches" correspond to the finite paths, because you are defining them based on specific nodes in specific levels, which mark the endpoints of the finite paths. You still don't have an algorithm for listing the infinite paths, because you haven't defined how to identify infinite paths.
>
> It is impossible to identify them by nodes.
No, it is impossible to identify them by a finite set of nodes. As long as you allow an infinite sequence of nodes, you can identify an infinite path. For example, the sequence R0̄ (zero repeating) is the unique infinite path that traces out the left edge of the tree, while R1̄ (one repeating) is its counterpart on the right edge.
Every infinite sequence of nodes (a_i) defines a unique infinite path, and every unique infinite path is defined by an infinite sequence of nodes (a_i).
> > You can't identify a unique infinite path based on a specific node, because there are an infinite number of unique infinite paths that pass through each node.
>
> Alas the paths of that infinite number cannot be distinguished.
Sure they can:
P1 = (a_i), defined for all i in N, where a_1 = R and a_i = 0 for all i > 1
P2 = (a_i), defined for all i in N, where a_1 = R, a_2 = 1, and a_i = 0 for all i > 2
These are both clearly infinite paths (because they have one node for every natural number), and they differ at node a_2, so they are distinguished.
> Look at the diagonal argument. There the anti-diagonal is distinct from all other reals by digits at finite places.
Not just at some finite places. At ALL of them. It differs from all of them in an infinite number of places.
> There is no digit beyond all finite palces.
Yes, this is sort of fundamental to why the reals are uncountable.
> But in the Binary Tree you cannot distinguish the believed paths at finite places.
I don't know what a "believed path" is, but since the infinite paths pass through an infinite number of nodes, they too cannot be distinguished if you only refer to specific finite positions. You must refer to full infinite sequences.
EFQ