List questions from examples-counterexamples

Published on 10 Apr 2026 - 0:37

474

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Continuous bijection whose inverse is not continuous at uncountably many points

Published on 12 Apr 2026 - 12:06

74

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Probability of result

Published on 12 Apr 2026 - 11:36

1.3k

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Counterexample for the Open Mapping Theorem

Published on 11 Apr 2026 - 4:59

1.5k

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Existence and uniqueness of limit of inverse function

Published on 15 Apr 2026 - 6:09

398

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Are there interesting examples of medial non-commutative semigroups?

Published on 11 Apr 2026 - 11:18

781

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Structures with addition, multiplication and exponentiation.

Published on 10 Apr 2026 - 20:35

158

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Do silly-rings exist?

Published on 15 Apr 2026 - 7:05

213

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An isometrie $\varphi: S_1\to S_2$ which cannot be extended into distance-preserving map

Published on 15 Apr 2026 - 8:10

85

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Does there exist a suitable function $f : \mathbb{N} \rightarrow \mathbb{N}$ such that $f(n^m) = mf(n)$? I think no.

Published on 15 Apr 2026 - 8:58

119

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The Tangent Disc Topology is developable

Published on 15 Apr 2026 - 19:55

1.7k

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Examples of root, parabolic, and borel subgroups corresponding to roots

Published on 14 Apr 2026 - 17:56

1.6k

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$X$ is homeomorphic to $X\times X$ (TIFR GS $2014$)

Published on 14 Apr 2026 - 17:11

345

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Non-trivial order on a set with infinitely many minimals/maximals

Published on 16 Apr 2026 - 16:05

24.8k

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Is $f(A)\cap f(B)$ a subset of $f(A\cap B)$?

Published on 15 Apr 2026 - 9:25

List Question

Does a matrix $A$ of $\pm1$'s of order $11$ exist with $\det A >4000$?

Continuous bijection whose inverse is not continuous at uncountably many points

Probability of result

Counterexample for the Open Mapping Theorem

Existence and uniqueness of limit of inverse function

Are there interesting examples of medial non-commutative semigroups?

Structures with addition, multiplication and exponentiation.

Do silly-rings exist?

An isometrie $\varphi: S_1\to S_2$ which cannot be extended into distance-preserving map

Does there exist a suitable function $f : \mathbb{N} \rightarrow \mathbb{N}$ such that $f(n^m) = mf(n)$? I think no.

The Tangent Disc Topology is developable

Examples of root, parabolic, and borel subgroups corresponding to roots

$X$ is homeomorphic to $X\times X$ (TIFR GS $2014$)

Non-trivial order on a set with infinitely many minimals/maximals

Is $f(A)\cap f(B)$ a subset of $f(A\cap B)$?

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