User Ashutosh

174 votes

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Does every non-empty set admit a group structure (in ZF)?

answered Jan 26, 2010 at 0:07

37 votes

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If any open set is a countable union of balls, does it imply separability?

answered Sep 19, 2014 at 2:37

19 votes

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How quickly can the derivative of an everywhere differentiable function change sign?

answered Apr 4, 2017 at 20:50

17 votes

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Sierpinski's construction of a non-measurable set

answered Dec 22, 2014 at 16:34

16 votes

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Does there exist an uncountable partition of a Polish space so that the union of any collection of blocks is Borel?

answered Aug 18, 2015 at 4:44

13 votes

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elementary equivalence of infinitary symmetric groups

answered Jan 10, 2010 at 1:20

12 votes

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Real-valued measurable cardinals

answered Jun 1, 2016 at 20:51

11 votes

A question of Erdős on entire functions

answered Aug 30, 2015 at 20:09

11 votes

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A Cohen real which always amalgamates with others

answered Sep 15, 2016 at 21:41

11 votes

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Minimum cardinality of lower-bounding subset of $[\omega]^\omega$

answered Jun 2, 2015 at 13:14

10 votes

A question about "small" uncountable cardinal numbers

answered May 4, 2014 at 15:58

10 votes

Translates of measure zero set

answered Oct 26, 2017 at 22:27

10 votes

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Can every dense subset be partitioned into two dense subsets?

answered Apr 17, 2018 at 17:55

10 votes

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Witness to a failure of Fubini/Tonelli

answered May 29, 2016 at 18:15

10 votes

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On the existence of a family of countably additive extensions of Lebesgue measure

answered Dec 20, 2019 at 9:49

9 votes

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Suslin trees in ccc ideals

answered Jan 31, 2014 at 1:46

8 votes

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Under $\neg CH$, have countable unions of rationally independent numbers inner measure zero?

answered May 11, 2015 at 17:25

7 votes

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A classic cardinal characteristic of the continuum in disguise?

answered Mar 27, 2015 at 14:22

7 votes

Additive Subgroups of the Reals.

answered Mar 29, 2011 at 16:40

7 votes

On the behaviour of $\sin(n!\pi x)$ when $x$ is irrational.

answered Aug 3, 2010 at 20:24

7 votes

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Can you have many independent reals?

answered Oct 14, 2015 at 5:03

7 votes

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How many closed measure zero sets are needed to cover the real line?

answered Dec 15, 2015 at 6:54

6 votes

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centeredness in forcing iterations

answered Nov 6, 2014 at 19:58

6 votes

Saturation of null ideal

answered Jun 14, 2015 at 16:51

6 votes

If $(X,\tau)$ has more than $1$ point and is $T_2$ and connected, do we have $|X| =|\tau|$?

answered May 21, 2018 at 17:08

6 votes

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Cohen real without a minimal support

answered Dec 12, 2016 at 13:13

6 votes

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Minimal cover v.s random reals

answered Mar 5, 2017 at 4:56

6 votes

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If $S_\mathbb N$ is partitioned into finitely many pieces, must one piece contain a "skew copy" of every countable group?

answered Sep 17, 2019 at 14:26

6 votes

Regular borel measures on metric spaces

answered Aug 11, 2010 at 23:48

5 votes

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Question about product topology

answered Jun 27, 2013 at 18:23

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59 Answers

Does every non-empty set admit a group structure (in ZF)?

If any open set is a countable union of balls, does it imply separability?

How quickly can the derivative of an everywhere differentiable function change sign?

Sierpinski's construction of a non-measurable set

Does there exist an uncountable partition of a Polish space so that the union of any collection of blocks is Borel?

elementary equivalence of infinitary symmetric groups

Real-valued measurable cardinals

A question of Erdős on entire functions

A Cohen real which always amalgamates with others

Minimum cardinality of lower-bounding subset of $[\omega]^\omega$

A question about "small" uncountable cardinal numbers

Translates of measure zero set

Can every dense subset be partitioned into two dense subsets?

Witness to a failure of Fubini/Tonelli

On the existence of a family of countably additive extensions of Lebesgue measure

Suslin trees in ccc ideals

Under $\neg CH$, have countable unions of rationally independent numbers inner measure zero?

A classic cardinal characteristic of the continuum in disguise?

Additive Subgroups of the Reals.

On the behaviour of $\sin(n!\pi x)$ when $x$ is irrational.

Can you have many independent reals?

How many closed measure zero sets are needed to cover the real line?

centeredness in forcing iterations

Saturation of null ideal

If $(X,\tau)$ has more than $1$ point and is $T_2$ and connected, do we have $|X| =|\tau|$?

Cohen real without a minimal support

Minimal cover v.s random reals

If $S_\mathbb N$ is partitioned into finitely many pieces, must one piece contain a "skew copy" of every countable group?

Regular borel measures on metric spaces

Question about product topology