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dfeuer
  • Member for 12 years, 6 months
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48 votes
2 answers
4k views

Existence of non-constant continuous functions

30 votes
6 answers
4k views

Motivation for/history of Jacobi's triple product identity

13 votes
1 answer
514 views

Unprovable unprovability

13 votes
3 answers
4k views

$\mathbb Q$ is not the direct product of two non-trivial groups.

12 votes
2 answers
4k views

How do you prove that the dunce cap is not a surface?

9 votes
1 answer
740 views

Significance of unique isomorphism

8 votes
1 answer
726 views

Examples of canonical projections that are not epimorphisms and canonical injections that are not [duplicate]

6 votes
3 answers
205 views

What should I do if I don't know where to start?

6 votes
2 answers
282 views

Is dependent choice necessary to prove every perfect compact Hausdorff space is uncountable?

6 votes
2 answers
1k views

Are there nice circumstances under which connectedness of interior and boundary imply connectedness?

6 votes
1 answer
6k views

Is there a simple proof that a power series can be differentiated term by term?

5 votes
2 answers
263 views

Axiom of Choice in Logic

5 votes
1 answer
3k views

What are the usual definitions of minimality and maximality with respect to an arbitrary relation?

5 votes
3 answers
3k views

Is total boundedness a topological property?

5 votes
3 answers
2k views

Fibered products in $\mathsf {Set}$

4 votes
1 answer
132 views

Cases where reflexivity is hard to prove

4 votes
1 answer
446 views

An alternative approach to constructing the free group.

3 votes
1 answer
481 views

Fibered coproducts in $\mathsf{Ab}$

3 votes
1 answer
808 views

Fibered coproducts in $\mathsf{Set}$

3 votes
1 answer
1k views

Divisors of orders of group elements

3 votes
1 answer
202 views

Is every discrete topological space orderable?

3 votes
1 answer
210 views

Cardinality definitions in variants of ZF theory, yet again

2 votes
0 answers
53 views

Facing mostly-faced decks

2 votes
3 answers
245 views

Hint on power sum coefficients

2 votes
0 answers
318 views

Proofs that quasicomponents of compact Hausdorff spaces are connected

2 votes
1 answer
77 views

Convergence of generalized sums of non-zero elements

2 votes
0 answers
108 views

What are the usual terms for different kinds of well-foundedness?

2 votes
1 answer
467 views

$G\times H\cong G$ with $H$ non-trivial

2 votes
2 answers
435 views

Notation for "parallel" morphisms in a diagram

1 vote
0 answers
271 views

There is a surjective homomorphism from $\Bbb Z * \Bbb Z$ onto $C_2*C_3$ [duplicate]