User Reveillark

9 votes

1 answer

396 views

Closure of an orbit and quotient topology

asked Oct 19, 2017 at 22:11

8 votes

1 answer

123 views

Mostowski collapse of generic extensions of countable elementary submodels

set-theory forcing

asked Feb 25, 2021 at 18:10

8 votes

1 answer

188 views

Skolem Hulls and countable elementary submodels of $H(\theta)$

set-theory

asked Jun 12, 2021 at 6:21

7 votes

0 answers

109 views

Use of Power Set in showing that the generic extension satisfies Replacement

set-theory forcing

asked Oct 19, 2019 at 22:01

7 votes

0 answers

640 views

Analytic function defined in the punctured unit disk real in the unit circle then $f(z)=\overline{f(1/\overline{z})}$

complex-analysis

asked Sep 23, 2015 at 0:23

7 votes

3 answers

123 views

If $\sum a_n = +\infty$, with $a_n ≥0$, then we can find two disjoint subseries diverging

calculus sequences-and-series

asked Jun 15, 2015 at 18:31

6 votes

1 answer

98 views

If $\tau$ is a name, is $\{\sigma:\Vdash \sigma=\tau\}$ a proper class?

set-theory forcing

asked Jan 1, 2021 at 5:07

6 votes

1 answer

78 views

Recursion theory in $\sf HC$

set-theory computability

asked Sep 24, 2021 at 17:44

5 votes

1 answer

88 views

Absoluteness of complexity of sets of reals

set-theory descriptive-set-theory

asked Oct 4, 2021 at 0:27

5 votes

1 answer

120 views

Random reals in Kamamori's "The Higher Infinite"

set-theory forcing

asked Nov 7, 2019 at 16:48

5 votes

1 answer

141 views

If $\omega_1$ is inaccessible to the reals, then every $\mathbf{\Sigma}_2^1$ set has the Baire property

set-theory forcing

asked Apr 19, 2019 at 14:52

5 votes

1 answer

147 views

Shooting a club is Baire

set-theory forcing

asked May 4, 2019 at 0:33

5 votes

1 answer

174 views

Proving that the curvature is given by $\kappa = \frac{\|\gamma ' \times \gamma ''\|}{\|\gamma '\|^3}$

differential-geometry curves

asked Sep 6, 2015 at 18:36

5 votes

0 answers

88 views

If $\alpha<\beta$ are ordinals, then $\Sigma_\alpha^0\subset\Sigma^0_\beta$

proof-verification descriptive-set-theory

asked Jul 31, 2016 at 18:16

4 votes

2 answers

1k views

Discrete Sets in Certain Metric Spaces are Countable

real-analysis metric-spaces

asked Oct 7, 2014 at 2:23

4 votes

1 answer

94 views

Reals and collapsing posets

set-theory forcing

asked Apr 3, 2019 at 2:34

4 votes

1 answer

78 views

If $P\in H_\kappa$ and $\Vdash_P \tau\in H_\kappa$, then there is $\bar\tau\in H_\kappa$ with $\Vdash_P \tau=\bar\tau$

set-theory forcing

asked Apr 15, 2020 at 20:10

4 votes

2 answers

76 views

Non-commutative algebra $A$ with a non-trivial maximal ideal $M$ such that $A/M$ is not a division algebra

abstract-algebra ring-theory examples-counterexamples noncommutative-algebra algebras

asked Sep 25, 2021 at 5:56

3 votes

2 answers

95 views

Proving $A \to \exists x B \Rightarrow \exists x (A\to B)$ if $x$ is not free in $A$

logic proof-theory

asked Sep 27, 2019 at 1:38

3 votes

0 answers

88 views

Uniformization in the Solovay model

set-theory forcing

asked Sep 2, 2020 at 1:27

3 votes

1 answer

60 views

Proving $\|x=y\|\cdot \|\phi(x)\|\le\|\phi(y)\|$ in Boolean valued models

set-theory boolean-algebra forcing

asked Jul 15, 2019 at 17:37

3 votes

0 answers

135 views

Condensation lemma in Devlin

set-theory

asked Sep 1, 2019 at 17:15

3 votes

3 answers

572 views

k-Cells are Connected

real-analysis metric-spaces connectedness

asked Nov 2, 2014 at 2:58

3 votes

2 answers

68 views

Question regarding specific limits

calculus limits

asked Jan 18, 2014 at 17:44

3 votes

1 answer

126 views

Looking for a proof of the (general) Salem-Zygmund theorem

reference-request descriptive-set-theory trigonometric-series

asked Aug 2, 2016 at 19:22

3 votes

0 answers

80 views

Bernstein sets are sets of uniqueness

descriptive-set-theory trigonometric-series

asked Aug 6, 2016 at 18:58

3 votes

3 answers

62 views

Finite open covers of a complex $C^{(1)}$ curve.

complex-analysis plane-curves

asked Nov 3, 2015 at 18:25

3 votes

1 answer

467 views

Showing that, at an elliptic point, a surface lies on one side of the tangent plane.

differential-geometry surfaces

asked May 13, 2016 at 16:05

3 votes

1 answer

137 views

If $f:X\to Y$ is continuous, then the induced map $F:K(X)\to K(Y)$ is continuous wrt the Vietoris topology

general-topology proof-verification descriptive-set-theory

asked Oct 5, 2016 at 13:41

3 votes

1 answer

105 views

If $1\le\lambda \le \kappa$ are cardinals, with $\kappa$ infinite and $\lambda<\text{cf}(\kappa)$, then every map $\lambda\to\kappa$ is bounded

elementary-set-theory proof-verification cardinals

asked Nov 16, 2016 at 14:55

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116 Questions

Closure of an orbit and quotient topology

Mostowski collapse of generic extensions of countable elementary submodels

Skolem Hulls and countable elementary submodels of $H(\theta)$

Use of Power Set in showing that the generic extension satisfies Replacement

Analytic function defined in the punctured unit disk real in the unit circle then $f(z)=\overline{f(1/\overline{z})}$

If $\sum a_n = +\infty$, with $a_n ≥0$, then we can find two disjoint subseries diverging

If $\tau$ is a name, is $\{\sigma:\Vdash \sigma=\tau\}$ a proper class?

Recursion theory in $\sf HC$

Absoluteness of complexity of sets of reals

Random reals in Kamamori's "The Higher Infinite"

If $\omega_1$ is inaccessible to the reals, then every $\mathbf{\Sigma}_2^1$ set has the Baire property

Shooting a club is Baire

Proving that the curvature is given by $\kappa = \frac{\|\gamma ' \times \gamma ''\|}{\|\gamma '\|^3}$

If $\alpha<\beta$ are ordinals, then $\Sigma_\alpha^0\subset\Sigma^0_\beta$

Discrete Sets in Certain Metric Spaces are Countable

Reals and collapsing posets

If $P\in H_\kappa$ and $\Vdash_P \tau\in H_\kappa$, then there is $\bar\tau\in H_\kappa$ with $\Vdash_P \tau=\bar\tau$

Non-commutative algebra $A$ with a non-trivial maximal ideal $M$ such that $A/M$ is not a division algebra

Proving $A \to \exists x B \Rightarrow \exists x (A\to B)$ if $x$ is not free in $A$

Uniformization in the Solovay model

Proving $\|x=y\|\cdot \|\phi(x)\|\le\|\phi(y)\|$ in Boolean valued models

Condensation lemma in Devlin

k-Cells are Connected

Question regarding specific limits

Looking for a proof of the (general) Salem-Zygmund theorem

Bernstein sets are sets of uniqueness

Finite open covers of a complex $C^{(1)}$ curve.

Showing that, at an elliptic point, a surface lies on one side of the tangent plane.

If $f:X\to Y$ is continuous, then the induced map $F:K(X)\to K(Y)$ is continuous wrt the Vietoris topology

If $1\le\lambda \le \kappa$ are cardinals, with $\kappa$ infinite and $\lambda<\text{cf}(\kappa)$, then every map $\lambda\to\kappa$ is bounded