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Jochen
  • Member for 11 years, 10 months
  • Last seen this week
17 votes
3 answers
2k views

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

9 votes
1 answer
223 views

How much bigger is the power set -- explicitly

9 votes
1 answer
391 views

Does Tychonov's theorem imply Zorn's lemma

6 votes
0 answers
92 views

Adjunction symbol

6 votes
2 answers
156 views

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

6 votes
1 answer
634 views

Binary expansions

6 votes
2 answers
4k views

Proof of the Ham-Sandwich theorem

5 votes
2 answers
1k views

Does the hairy ball theorem follow from Borsuk-Ulam?

5 votes
1 answer
481 views

Compact subsets of the plane with connected complement

4 votes
1 answer
354 views

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

4 votes
1 answer
598 views

Quotient of a triangle

4 votes
2 answers
165 views

Are epimorphisms in the category of magmas surjective?

3 votes
1 answer
287 views

Convexity of $x^p$ -- without calculus

2 votes
1 answer
50 views

Linear after change of variables

2 votes
2 answers
235 views

How to make categorical limits unique?

2 votes
0 answers
196 views

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

2 votes
0 answers
55 views

Empty faces in $\Delta$-complexes

2 votes
1 answer
146 views

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

0 votes
1 answer
68 views

Can the increasing union of open disconnected sets be connected?

0 votes
1 answer
262 views

Geometric interpretation of alternating bilinear forms as an oriented area

0 votes
1 answer
255 views

Cusps and corners of smoothly parametrized curves

0 votes
0 answers
42 views

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