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# Questions

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vote
1
179
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### An action or two of $SL_2(\Bbb Z)$?

apr 25 at 7:54 Artur Jackson 113

1
14
3
766
views

### Research level applications of “row rank = column rank”?

feb 28 at 20:01 David Feldman 11.3k22579

2
11
3
993
views

### Cantor’s diagonal argument and ZF

feb 27 at 18:15 François G. Dorais 22.4k248113

6
10
3
807
views

### Games that never begin

nov 13 at 13:51 Joel David Hamkins 74.9k7187343

11
28
11
2k
views

### Important open problems that have already been reduced to a finite but infeasible amount of computation

nov 14 at 9:06 Nick Gill 2,881718

6
18
3
467
views

### An equivalence relation on group actions

oct 27 at 12:28 Yves Cornulier 2,9161611

1
4
0
129
views

### Almost universal properties

oct 24 at 19:58 David Feldman 11.3k22579

1
7
0
384
views

### Is every $\sigma$-algebra of sets *abstractly* the Borel algebra of a topology on perhps some other set?

oct 15 at 1:23 Joel David Hamkins 74.9k7187343

3
5
0
209
views

### Closure properties of familes of $G_\delta$ sets.

oct 8 at 23:05 David Feldman 11.3k22579

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