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user10
  • Member for 13 years, 5 months
  • Last seen more than 5 years ago
51 votes
4 answers
7k views

No continuous function switches $\mathbb{Q}$ and the irrationals

32 votes
2 answers
6k views

Isomorphism between complex numbers minus zero and unit circle

18 votes
1 answer
11k views

Rationals are not locally compact and compactness

16 votes
4 answers
4k views

Dense and locally compact subset of a Hausdorff space is open

13 votes
1 answer
5k views

Hausdorff locally compact and second countable is $\sigma$-compact

12 votes
2 answers
303 views

Are sets given in parametric form always algebraic?

11 votes
2 answers
3k views

Graph of a function homeomorphic to a space implies continuity of the map?

11 votes
3 answers
8k views

Finding number of matrices whose square is the identity matrix

10 votes
3 answers
3k views

$k[x]$-module and cyclic module over a finite dimensional vector space

9 votes
2 answers
662 views

Connectedness problem: sequences of points with distances at most $\varepsilon$

9 votes
2 answers
425 views

Uncountable family of uncountable compact subsets of $\mathbb{R}$

8 votes
3 answers
2k views

Notation for the set of all finite subsets of $\mathbb{N}$

8 votes
3 answers
930 views

$F_\sigma$-subsets in a normal space can be separated

8 votes
3 answers
6k views

Intersection maximal ideals of a polynomial ring

8 votes
1 answer
809 views

Diagonal in projective space

8 votes
1 answer
4k views

Find Zariski closure of a set

8 votes
1 answer
2k views

Recalling result of tensor product of polynomial rings

7 votes
3 answers
587 views

Stone Cech compactification of the naturals a cts image of the Cantor set?

7 votes
1 answer
732 views

Basic questions about $\mathbb{Z}^{\mathbb{N}}$ with the product topology

7 votes
1 answer
3k views

Is the set of fixed points in a non-Hausdorff space always closed?

7 votes
2 answers
426 views

Groups such that every finitely generated subgroup is isomorphic to the integers

7 votes
3 answers
1k views

Does localization preserves dimension?

7 votes
3 answers
935 views

Terminal object implies projection is an isomorphism

6 votes
2 answers
1k views

Showing $\mathbb{Z}_6$ is an injective module over itself

6 votes
2 answers
2k views

Existence of a matrix, characteristic polynomial and minimal polynomial

6 votes
3 answers
2k views

Local compactness exercise

6 votes
1 answer
992 views

Hypersurface becomes an hyperplane after embedding

5 votes
1 answer
655 views

Product of sigma compact spaces

5 votes
1 answer
866 views

Base of clopen and $T_{0}$ implies $X$ is Tychonoff

5 votes
3 answers
695 views

Connectedness problem and countability of compact subsets of the Sorgenfrey line

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