List questions from general-topology

Published on 11 Apr 2026 - 21:32

58

Views

How to find the mapping class groups of the tori $T^3$ and $T^4$?

Published on 13 Apr 2026 - 12:44

404

Views

$\epsilon$ fattening of an open set needn't be open

Published on 10 May 2026 - 12:39

39

Views

How do I prove the $f:X\to I$ by $f(x)=\min\{f_i(x_{\beta_i}):i=1,2,...,n\}$ is continuous.

Published on 10 May 2026 - 23:31

63

Views

Sets and supremum

Published on 14 Apr 2026 - 20:50

52

Views

If A is not $F_\sigma$ set, then subset of A is not $F_\sigma$ set

Published on 14 Apr 2026 - 19:12

64

Views

If in a given topological space X every set $ \{x\}, x \in X, $ is open, is then $X$ discrete

Published on 14 Apr 2026 - 3:40

73

Views

$F = \nabla f $ for some smooth $f: B \rightarrow \mathbb{R}$

Published on 16 Apr 2026 - 5:23

391

Views

Group of homeomorphism of [0,1]

Published on 12 Apr 2026 - 11:11

324

Views

Continuous function defined on (0,1) to {0,1}

Published on 10 Apr 2026 - 23:40

170

Views

Is every $\sigma$-algebra a Borel $\sigma$-algebra?

Published on 11 May 2026 - 6:34

142

Views

Almost clopen sets

Published on 14 May 2026 - 2:10

67

Views

Is the function $ f \colon X \to f(X), f(x) =x^3 $ continuous, uniformly continuous

Published on 13 Apr 2026 - 1:16

100

Views

Showing that $g(T)\subseteq f'(I) \subseteq\overline{g(T)}$ where $g(x,y) = \frac{f(x) - f(y)}{x-y}$

Published on 17 Apr 2026 - 15:15

811

Views

Showing $\{(x, y) : x^{2} > y\}$ is an open set

Published on 06 Apr 2026 - 10:18

List Question

Exchanging limits when functions may not converge uniformly

How to find the mapping class groups of the tori $T^3$ and $T^4$?

$\epsilon$ fattening of an open set needn't be open

How do I prove the $f:X\to I$ by $f(x)=\min\{f_i(x_{\beta_i}):i=1,2,...,n\}$ is continuous.

Sets and supremum

If A is not $F_\sigma$ set, then subset of A is not $F_\sigma$ set

If in a given topological space X every set $ \{x\}, x \in X, $ is open, is then $X$ discrete

$F = \nabla f $ for some smooth $f: B \rightarrow \mathbb{R}$

Group of homeomorphism of [0,1]

Continuous function defined on (0,1) to {0,1}

Is every $\sigma$-algebra a Borel $\sigma$-algebra?

Almost clopen sets

Is the function $ f \colon X \to f(X), f(x) =x^3 $ continuous, uniformly continuous

Showing that $g(T)\subseteq f'(I) \subseteq\overline{g(T)}$ where $g(x,y) = \frac{f(x) - f(y)}{x-y}$

Showing $\{(x, y) : x^{2} > y\}$ is an open set

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