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A shy, neither amateur nor high-class, mathematician from Colombia.


Jul
16
comment Galois closure of $\mathbb{C}(T,\sqrt{T^2+T+1})$ over $\mathbb{C}(T^3)$
The phrasing "$\mathbb C(T)$ be a function field" is a bit misleading: by definition an algebraic function field in one variable over a field $k$ (briefly, a function field over $k$) is a finite field extension of the rational function field $k(T)$.
Jul
15
accepted Can a group with exactly five subgroups be nonabelian?
Jul
15
awarded  Citizen Patrol
Jul
7
comment The largest value of $k$ for $\Bbb{Z}^{k}$ to be embedded in $\mathcal{GL}(n,\Bbb{Z})$.
In other words, you are asking about the maximum rank of a free abelian subgroup of $\mathcal{GL}(n,\mathbb Z)$. By the way, why did you include the [finite-groups] tag?
Jul
6
comment Proving that tensoring a projective module with a flat module gives a projective module?
You are right: if $F$ is free, say $F=R^{\oplus I}$, then $M\otimes_RF$ is just $M^{\oplus I}$, which is not free in general.
Jul
3
comment Germs of $C^\infty$ functions near $0$ vs. germs of infinitely differentiable functions at $0$
@DanielFischer Thanks a lot for your partial answer.
Jul
3
revised Germs of $C^\infty$ functions near $0$ vs. germs of infinitely differentiable functions at $0$
added 52 characters in body
Jul
3
comment Germs of $C^\infty$ functions near $0$ vs. germs of infinitely differentiable functions at $0$
@DanielFischer Yes, I am interested in the algebraic properties. Regarding the complex case, you catch me, I naively thought that complex differentiability at $0$ implies differentiability of all order. I am going to edit the question.
Jul
3
revised Germs of $C^\infty$ functions near $0$ vs. germs of infinitely differentiable functions at $0$
added 219 characters in body
Jul
3
reviewed Approve suggested edit on Find the probability of selecting an ordered pair from set $S$
Jul
3
asked Germs of $C^\infty$ functions near $0$ vs. germs of infinitely differentiable functions at $0$
Jul
2
awarded  Curious
Jun
23
comment Prove that every sum of squares in $K$ is a square in $K$, where $K$ is certain field.
Hint: $a^2+b^2=(a+bi)(a-bi)$.
Jun
16
reviewed Approve suggested edit on How can I find the roots of a quartic equation, knowing one of its roots?
Jun
12
reviewed Approve suggested edit on Given two integrals, evaluate four different ones on different intervals?
Jun
12
reviewed Approve suggested edit on calculate radius of convergence
Jun
12
reviewed Approve suggested edit on Number of digits of the number of digits of the number of digits of $2014^{2014}$
Jun
10
reviewed Approve suggested edit on Help Me Understand: Proof that Finite Intersection of Open Sets is Open
Jun
6
reviewed Approve suggested edit on Determine range of $\rho$ in correlation matrix
May
30
comment Let $V $be a vector space. Prove/Disprove: There is a norm $\|\cdot\|$, such that all subsets of $V$ are open sets in $(V,\|\cdot\|)$.
@Neal I would say Mideast instead... but actually with Internet cardinal points are less relevant.