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Msc student at the university of Amsterdam. Main interests: algebraic and complex geometry, algebraic topology.

Also see: http://www.science.uva.nl/math/People/show_person.php?Person_id=Ronde+J.J.J.+de


Jul
24
comment $x^y < y^x$ for $y\ll x$?
Very good answer!
Jul
20
comment Formal construction of $\mathbb Q$: interpretation and equality of elements
One does not really say that $n$ and $(n,1)$ are strictly equal. However, there is a natural injective morphism from $\mathbb{Z}$ to $\mathbb{Q}$ as you just constructed it, where $n$ is sent to $(n,1)$. In this way we identify $\mathbb{Z}$ with this particular subset of $\mathbb{Q}$.
Jul
18
awarded  Yearling
Jul
13
awarded  Nice Question
Jul
2
awarded  Curious
Jul
2
awarded  Inquisitive
Jun
25
comment Checking derivation of y = a^x
A nitpick, use curly brackets like x^{-1} instead of x^-1 as you used... Otherwise very nice!
May
16
awarded  Nice Question
May
7
comment What is the integral of n-th root of tan x?
Ah, i was too quick, sorry for the hassle!
May
7
comment What is the integral of n-th root of tan x?
I think there's a typo, in the first displayed line of math you wrote $y^{1/n} = z^n$, but by definition of your $z$ that should be $y^{1/n} = z$ (its in the integral sign, you see what i mean?)
Apr
21
comment Triple Cover of the Riemann Sphere
Hi! Is this homework?
Apr
12
comment Is $i \in \mathbb{Q}[\sqrt[4]{-2}]$?
Ah, writing out $\text{cis}(\pi/4)$ explicitly escaped me. Thanks for clearing that up!
Apr
12
comment Is $i \in \mathbb{Q}[\sqrt[4]{-2}]$?
Nice answer, but could you clarify how $\sqrt[4]{-2} \in \mathbb{Q}(\sqrt[4]{2},i)$? It is not clear to me. Thanks a bunch! Not that it is really necessary by the way, your reasoning shows $\mathbb{Q}(\sqrt[4]{2},i) \subseteq \mathbb{Q}(\sqrt[4]{-2})$ which is enough to reach your conclusion.
Mar
31
comment What is the cokernel of $\Bbb Q^{\text{disc}} \hookrightarrow \Bbb R$?
Thanks for clarifying that!
Mar
31
comment What is the cokernel of $\Bbb Q^{\text{disc}} \hookrightarrow \Bbb R$?
Dear Zhen Lin, i am just reading this question out of interest but am unfamiliar with the notation $\mathbb{R}^{\text{disc}}$. Could you maybe clarify that? Just out of curiosity..
Mar
31
awarded  Revival
Mar
26
comment Using the definition of a limit
I think you switched order in the definition of your limit.. Also the limit here expresses continuity of the function $f$ at the point $a$, is this really what you want?
Mar
16
comment Why is $\pi_1(X,x_0)$ a group?
As a side note to anyone who wants to check out the gluing lemma on wikipedia (it's called the pasting lemma there by the way): imho the reasoning there does not seem fully satisfactory. So be careful in copying their reasoning. (And feel free to disagree with me :) ) Anyway, the result is true of course that's the most important part here.
Mar
16
comment A basic book on (discrete) 2D - Fourier transforms?
I borrowed Gonzales and Woods, it is very nice. However, do you know where to find something about directional and orientation filters?
Mar
11
comment Prove $X=(y^{2}z-x^{3}+xz^{2})\backslash\{(1,0,-1)\}$ is irreducible.
I guess if $f = y^2z - x^3 +xz^2$ were reducible, $Z(f)$ should split in at least two components, and $Z(f)$ should be singular where they meet. Since there is just one singular point, the components must meet in exactly that point. By Bezout, the components are either a degree 2 curve and a line meeting transversally at the point, or three lines all meeting eachother in the same point. I guess that gives enough restrictions on $f$. However, Bezout only works if $k$ is algebraically closed, so i hope that was indeed an assumption we could make.