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I'm a student of mathematics in Germany.


May
1
comment Equivalent characterizations of group objects
@Hurkyl It may be that others visiting this site still need to do the exercise. On the other hand, … 11 views.
May
1
revised Equivalent characterizations of group objects
added 128 characters in body
May
1
revised Equivalent characterizations of group objects
added 98 characters in body
May
1
asked Equivalent characterizations of group objects
Apr
30
answered Suppose $z \neq -1$ is a complex number of norm 1. Prove that $(\frac{1+z}{|1+z|})^2 =z $
Apr
30
awarded  Cleanup
Apr
29
comment Exponents in Identities
I’ve edited the formula – is that what you meant?
Apr
29
revised Exponents in Identities
added 17 characters in body
Apr
28
comment Modules over commutative rings
Other than that, $xr$ for $x ∈ M$, $r ∈ R$ makes no sense if there’s no way to interpret $M$ as a right $R$-module.
Apr
28
comment Modules over commutative rings
One thing you should know: There’s a notion of an opposite Ring $R^{\mathrm{op}}$ of any ring $R$. Basically, $R^{\mathrm{op}} = R$ except multiplication is reversed, so define $R^{\mathrm{op}} = (R,·_\mathrm{op})$ where $a·_{\mathrm{op}}b$ computes to $ba$. It’s easy to show that if $M$ is a left $R$-module, then $M$ is a right $R^{\mathrm{op}}$-module, and $R = R^\mathrm{op}$ if and only if $R$ is commutative. There are many rings isomorphic to their opposite rings – so for them any left module also carries a structure of a right module.
Apr
27
answered Irreducibility over $ \mathbb{Q} ( \sqrt{2} , \sqrt{3})$
Apr
26
comment Surjective Homomorphic map and orders
Can I downvote for bad jokes? : – /
Apr
26
revised Classification of semidirect products
changed the notation.
Apr
25
answered Classification of semidirect products
Apr
25
comment Classification of semidirect products
Where is this question coming from? Is this homework?
Apr
23
revised Pumping lemma contradiction
tex formatting
Apr
23
comment Pumping lemma contradiction
How about $b^pa^{p+1}$ instead?
Apr
23
revised Ring Properties
added 17 characters in body
Apr
23
answered Ring Properties
Apr
19
comment Algebra, Geometry and Algebraic Geometry
My understanding (probably naïve): Algebra deals with structures and equations, geometry deals with spaces and figures and algebraic geometry combines structures with spaces and equations with figures.