Skip to main content
Jochen's user avatar
Jochen's user avatar
Jochen's user avatar
Jochen
  • Member for 11 years, 10 months
  • Last seen this week
6 votes
0 answers
92 views

Adjunction symbol

2 votes
2 answers
235 views

How to make categorical limits unique?

6 votes
2 answers
156 views

Are all compact subsets of $\mathbb R^{\mathbb R}$ separable?

2 votes
1 answer
146 views

A wrong interpretation of Whitney's theorem that $C^1$-manifolds are smooth manifolds

2 votes
0 answers
55 views

Empty faces in $\Delta$-complexes

9 votes
1 answer
391 views

Does Tychonov's theorem imply Zorn's lemma

4 votes
2 answers
165 views

Are epimorphisms in the category of magmas surjective?

0 votes
1 answer
68 views

Can the increasing union of open disconnected sets be connected?

2 votes
0 answers
196 views

Pairs of notation: Which one is the co-thing?

0 votes
1 answer
262 views

Geometric interpretation of alternating bilinear forms as an oriented area

9 votes
1 answer
223 views

How much bigger is the power set -- explicitly

4 votes
1 answer
598 views

Quotient of a triangle

4 votes
1 answer
354 views

Why is the Klein bottle not homeomorphic to a subspace of $\mathbb R^3$?

0 votes
0 answers
42 views

Inverse of square matrix -- just by calculation [duplicate]

0 votes
1 answer
255 views

Cusps and corners of smoothly parametrized curves

5 votes
2 answers
1k views

Does the hairy ball theorem follow from Borsuk-Ulam?

3 votes
1 answer
287 views

Convexity of $x^p$ -- without calculus

17 votes
3 answers
2k views

Spectral theorem for unbounded self-adjoint operators on REAL Hilbert spaces

5 votes
1 answer
481 views

Compact subsets of the plane with connected complement

2 votes
1 answer
50 views

Linear after change of variables

6 votes
2 answers
4k views

Proof of the Ham-Sandwich theorem

6 votes
1 answer
634 views

Binary expansions