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Jochen
  • Member for 10 years, 1 month
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14 votes
3 answers
2k views

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

9 votes
1 answer
206 views

How much bigger is the power set -- explicitly

6 votes
1 answer
628 views

Binary expansions

6 votes
2 answers
3k views

Proof of the Ham-Sandwich theorem

5 votes
2 answers
996 views

Does the hairy ball theorem follow from Borsuk-Ulam?

5 votes
1 answer
400 views

Compact subsets of the plane with connected complement

5 votes
1 answer
500 views

Quotient of a triangle

4 votes
2 answers
141 views

Are epimorphisms in the category of magmas surjective?

4 votes
1 answer
279 views

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

4 votes
2 answers
100 views

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

3 votes
1 answer
237 views

Convexity of $x^p$ -- without calculus

2 votes
1 answer
46 views

Linear after change of variables

2 votes
1 answer
74 views

How to make categorical limits unique?

2 votes
0 answers
108 views

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

0 votes
1 answer
48 views

Can the increasing union of open disconnected sets be connected?

0 votes
1 answer
132 views

Geometric interpretation of alternating bilinear forms as an oriented area

0 votes
1 answer
170 views

Cusps and corners of smoothly parametrized curves

0 votes
0 answers
39 views

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