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Johannes Hahn's user avatar
Johannes Hahn's user avatar
Johannes Hahn
  • Member for 13 years, 11 months
  • Last seen more than a week ago
  • Aachen, Germany
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About

Studied math, PhD, was a software developer / tech consultant for a while, returned to university as a PostDoc, now software developer again. Still a mathematician at heart.

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All Questions Answers
Score Newest
answer
45
Fantastic properties of Z/2Z
Nov 14, 2013
answer
40
Problems where we can't make a canonical choice, solved by looking at all choices at once
Dec 21, 2010
answer
23
Is cohomology always related to topology?
Jun 9, 2021
answer
20
For nonabelian finite simple $G$, does $Aut(G)$ have a unique subgroup isomorphic to $G$?
Feb 19, 2019
question
19
Are there Hamilton paths in Cayley graphs of Coxeter groups?
Mar 20, 2012
answer
18
Can we actually find any fixed points with Brouwer's theorem?
Aug 29, 2012
answer
18
Nonequivalent definitions in Mathematics
Nov 22, 2017
answer
17
Interesting applications (in pure mathematics) of first-year calculus
Aug 10, 2010
answer
16
Is every commutative group structure underlying at least one (unitary, commutative) ring structure
Jan 18, 2014
answer
15
Free ordered field?
Oct 28, 2019
Top Meta posts
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10
How much is MathOverflow exposed to recent events on StackExchange?
7
Request: Add the option to close to review tasks from the "first questions" queue
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24
Odd digits of $2^n$
21
What functions are support functions of convex sets
15
Getting the most general form of Mayer-Vietoris from the axioms of homology
12
Sheaf as a functor
11
Category theory with multisets

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