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I'm a student of mathematics in Germany.


Aug
13
revised How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
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Aug
13
revised How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
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Aug
13
revised How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
fixed definition of π
Aug
13
revised How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
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Aug
13
answered How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
Aug
13
comment How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
Do I understand you correctly in that you want to know how to construct a group extension from a $2$-cocycle?
Aug
13
comment How can I find $\mathbb Z_4$ as an extension of $\mathbb Z_2$ by $\mathbb Z_2$?
What is $FS$ and $IFS$?
Aug
12
comment Understanding the proof of: If $|A| = \kappa$, then $|\mathcal{P}(A)|=2^{\kappa}$.
I wouldn’t call it a mistake. I think the author uses “$f\colon X → χ_X$” for “$f\colon X ↦ χ_X$”.
Aug
11
comment If $\sum a_n$ converges and $b_n=\sum\limits_{k=n}^{\infty}a_n $, prove that $\sum \frac{a_n}{b_n}$ diverges
Is this homework, though?
Jul
20
comment Are there any well known mathematicians who published very little?
I don’t know how much Hermann Grassmann published, but he might be a candidate: I believe he is only known for his Lineare Ausdehnungslehre in which he conceived of linear and multilinear algebra (including the exterior product).
Jul
2
awarded  Curious
Jul
1
comment How to proof (using by mathematical induction)($n\in \mathbb{N}$)
@user159813 $\frac 1 n \overset{n → ∞} \longrightarrow 0$, but $\frac 1 n > 0$, so $0 > 0$?
Jun
30
comment If $AB = I$ then $BA = I$: is my proof right?
It’s not correct – see Thomas’ comment. And @agha: I think she or he is more interested in finding an own proof.
Jun
29
comment Is there anything behind the “$m + N$” notation for elements in the factor structure $M/N$?
@AndreasCaranti Okay, thank you. So do you know whether there’s anything behind this notation or do you know of any alternative notations?
Jun
29
comment Is there anything behind the “$m + N$” notation for elements in the factor structure $M/N$?
@AndreasCaranti No, not particularly. It only tells me that the partition of $M$ into $N$-cosets in $M$ is a realization of the factor structure $M/N$. Okay, this can be very useful from time to time – but most of the time, it’s not what I need, so why should I accent it through my notation?
Jun
29
asked Is there anything behind the “$m + N$” notation for elements in the factor structure $M/N$?
Jun
8
awarded  Fanatic
May
31
answered If number of homomorphisms from $G \mapsto H$ is $n$. How many homomorphisms are there from $G \oplus G\cdot\cdot \cdot \oplus~ G ( s $ times) to $H$
May
31
comment If number of homomorphisms from $G \mapsto H$ is $n$. How many homomorphisms are there from $G \oplus G\cdot\cdot \cdot \oplus~ G ( s $ times) to $H$
Why and for which $Ψ$ do you have $|G/\operatorname{ker} Ψ| = n$?
May
21
comment Embeddings $A → B → A$, but $A \not\cong B$?
Thanks. What would you consider as structure preserving maps?