Mathematics
mathcounterexamples.net's user avatar
mathcounterexamples.net's user avatar
mathcounterexamples.net's user avatar
mathcounterexamples.net
  • Member for 8 years, 11 months
  • Last seen this week
Profile Activity
Stats
69,389
reputation
1.1m
reached
2,819
answers
118
questions
Communities
View all
About

I'm living in Paris, France and doing Math as a hobby, with special interest in Mathematical logic and Analysis.

I opened in July 2014 a website dedicated to Math Counterexamples. I welcome any suggestion for additional counterexamples... at least at a level that I can understand!

My LinkedIn page. A long time ago I programmed some modules of CATIA a famous computed aided design solution.

Badges
View all badges
5
gold badges
37
silver badges
103
bronze badges
Top tags
View all tags
1,122
Score
672
Posts
23
Posts %
639
Score
355
Posts
12
Posts %
591
Score
384
Posts
13
Posts %
378
Score
225
Posts
8
Posts %
326
Score
213
Posts
7
Posts %
308
Score
159
Posts
5
Posts %
Top posts
View all questions and answers
All Questions Answers
Score Newest
question
30
Group $G$ whose center $Z(G)$ is cyclic and with $G/Z(G)$ commutative
Jun 28, 2015
answer
23
Proof: Is there a line in the xy plane that goes through only rational coordinates?
Dec 12, 2015
answer
20
Proof that the number of proofs is countably infinite
Jun 11, 2018
answer
18
Is $F=\left\lbrace f: f\in C_{\left[0, 1\right]}, f\left(0\right)=f\left(1\right)\right\rbrace$ complete metric space?
Jun 28, 2018
answer
18
$ \bigcup_{n=1}^{\infty}\{z\in\Bbb C:z^n=1\}=\{z\in\Bbb C:|z|=1\}$?
Feb 1, 2019
answer
17
How to check if a function is convex
Aug 16, 2019
answer
16
Convergence of infinite sum (factorial and root)
Nov 22, 2016
question
16
$a_n =0$ for all $n \in \mathbb N$ if $\sum a_n^k =0$ for all integers $k \ge 1$
Sep 13, 2015
answer
15
A+B is closed if one of them is compact
Sep 5, 2015
answer
15
can polynomial functions with rational coefficients approximate any continuous function on $[a,b]$.
Aug 30, 2018
Top network posts
View all network posts
66
Results true in a dimension and false for higher dimensions
36
Why does this sequence converges to $\pi$?
18
What are your favorite instructional counterexamples on sequences?
14
ODE properties true in finite dimension but not in Banach spaces of infinite dimension
10
Probability over a plane

Your privacy

By clicking “Accept all cookies”, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy.