Timeline for A set for which it is hard to determine whether or not it is countable.
Current License: CC BY-SA 2.5
7 events
| when toggle format | what | by | license | comment | |
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| Mar 24, 2011 at 4:01 | comment | added | fedja | @George. Yes, this is the quickest way to see it. @mathahada The set is actually pretty exotic even if it is what most people believe it is. If you don't believe me, just try to answer the question whether it is closed. | |
| Mar 23, 2011 at 13:17 | comment | added | George Lowther | @Laurent: Well, they are all computable numbers. Also someone asked about this on math.stackexchange. I'm not sure whether it is the same as Fedja's "next to obvious" answer, but I posted mine as an answer math.stackexchange.com/questions/28543/… | |
| Mar 23, 2011 at 12:36 | comment | added | Laurent Berger | @fedja: I must be right there with those poor grad students. Can you maybe give a hint? | |
| Mar 23, 2011 at 10:50 | comment | added | mathahada | I thought I solved this until I've seen fedja's comment. The subset in question is not very exotic, its just described in an obscure way (like writing "the set of all non trivial solutions for x^3+y^3=z^3" for the empty set)... | |
| Mar 23, 2011 at 5:10 | comment | added | Charles Staats | Sorry, I just realized my "solution" relied on the fact that the quotient of two integers is an integer. | |
| Mar 22, 2011 at 18:49 | comment | added | fedja | Obvious subset? It is not even known whether it is a subset of algebraic numbers! :) | |
| Mar 22, 2011 at 3:19 | history | answered | fedja | CC BY-SA 2.5 |