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Jan
26
comment If $M$ is normal and $M \cap U = U'$ for some special subgroup $U$, then $M / G'$ is a Hall-subgroup of $G / G'$.
ok, that makes more sense
Jan
26
comment If $M$ is normal and $M \cap U = U'$ for some special subgroup $U$, then $M / G'$ is a Hall-subgroup of $G / G'$.
What are the conditions on $G'$? Is it just a normal subgroup of $G$ that is contained in $M$? If so, then it is enough to show for $G'=\{e\}$, but then you have no condition on $M$ other than it is normal in $G$. In any way, it seems that the group $G'$ is irrelevant for the proof.
Jan
21
comment Ring of matrices isomorphic to $O := \left\{a+b\frac{1+\sqrt{D}}{2}: a, b \in \mathbb{Z} \right\}$
@J.G edited my answer
Jan
21
revised Ring of matrices isomorphic to $O := \left\{a+b\frac{1+\sqrt{D}}{2}: a, b \in \mathbb{Z} \right\}$
full proof
Jan
21
answered Ring of matrices isomorphic to $O := \left\{a+b\frac{1+\sqrt{D}}{2}: a, b \in \mathbb{Z} \right\}$
Jan
21
answered Representation of invertible elements in the Total ring of fractions
Jan
5
answered Maximal number of partial limits
Jan
5
reviewed Approve Maximal number of partial limits
Jan
4
comment Importance of diagonal (topology)
@MikeMiller while I am a bit rusty on my algebraic geometry, I do remember that every affine scheme should be separated, which is the "right" analog for Hausdorffness in algebraic geometry.
Jan
4
answered Are these two statements involving inf and sup equivalent?
Jan
4
answered Importance of diagonal (topology)
Jan
4
revised Embedding fields into the complex numbers $\mathbb{C}$.
edited title
Jan
3
comment The central product of two cyclic subgroups of prime power order for one $p$ is isomorphic to direct product of two cyclic groups of prime power order
@Stefan I think that generators and relations is the easiest way to present this solution. The main idea here was to choose a new "basis" for the group and use the relations in order to figure out the right basis to choose.
Jan
3
answered The central product of two cyclic subgroups of prime power order for one $p$ is isomorphic to direct product of two cyclic groups of prime power order
Jan
3
answered Automorphism of cyclic $p$-group
Jan
2
revised In $a^n \equiv b^n \pmod m$, does $n$ have to be an integer?
added 109 characters in body
Jan
2
comment In $a^n \equiv b^n \pmod m$, does $n$ have to be an integer?
@ThomasAndrews You are correct. Though in this case, if $m$ is prime then it is well defined whenever you don't take the inverse of zero.
Jan
2
answered In $a^n \equiv b^n \pmod m$, does $n$ have to be an integer?
Jan
2
answered Is my solution correct? (primes of the form $a^2+b^2d$ and their principal ideals)
Jan
1
comment Finding the limit of the sequence $(1 - 1/\sqrt 2) \dotsm ( 1 - 1/\sqrt {n+1})$
Your inequalities are in the wrong direction