upquark
Joined 14 years ago
Joined 14 years ago
> In January 1920, Mustafa Kemal advanced his troops into Marash where the Battle of Marash ensued against the French Armenian Legion. The battle resulted in a Turkish victory alongside the massacres of 5,000–12,000 Armenians spelling the end of the remaining Armenian population in the region.
He finished off the Cilician Armenians from Anatolia, whoever was left under French protection and had escaped the Genocide.
I'm saying that ^ sentence makes no sense to me, I don't know how to parse it formally. If you start talking about the set of "definable" numbers (not computable, but specifically "definable"), I believe you're gonna run into paradoxes as it's an ill-defined concept, similar (in spirit) to "all integers described under 100 words". In fact, the linked article actually talks about it in 2.3.
> For any given language, like for instance ZFC, we can say that definable numbers are a countable subset. Hence measure zero.
If I can describe a set of objects, then we're all set as far as I'm concerned (mathematically speaking). Being able to efficiently construct individual elements of this set using Turing machines or other computational devices is an orthogonal problem.
Also, I don't think having only countable number of utterances in ZFC precludes you from having well-defined uncountable sets described in that system (quite obviously, for any set S take 2^S which is very well-defined).
I am leaving out any linguistic or Turing-computability aspects out of this, and people try to bring it back in, mixing computability with definability.
For instance, Chaitin's constant is a perfectly well-defined number, albeit uncomputable by construction: https://en.wikipedia.org/wiki/Chaitin%27s_constant
Either way, my point above was that this entire branch is not "mainstream math" by any means, AFAIK
The way you defined that number makes it a perfectly valid element of the set R, as described by, say, the axiomatic definition here:
https://en.wikipedia.org/wiki/Real_number#Axiomatic_approach
Whether it's easy or hard or computationally intractable to compare it to other numbers, that's a totally different question unrelated to its definition.
Plus, you can actually empirically compute a finite set of initial digits (a specific Turing machine can be analyzed to see if it terminates or not), so you can compare this number with one that's constructed by flipping its digits, or with pi, etc.
See, I claim that this set is ill-defined, so I can't know its properties like whether or not it's dense, open, closed, Borel-measurable, etc. etc.
You have to tell me what its properties are, and I will come up with a concrete proof that the set in question is ill-defined.
EDIT: After I RTFA'd, this is actually the paradox in section 2.3 of the linked article
In my view, every real number is well-defined and there's nothing controversial about the set of real numbers. If the infinite aspect of it causes some researchers to call it a "mathematical fantasy", so be it, so is literally every other mathematical model we use in our lives.
That's mine too, but nowadays teams and especially managers last about 6 months in one place. What is one supposed to do?