4,712 reputation
917
bio website motls.blogspot.com
location Czech Republic
age 40
visits member for 3 years, 5 months
seen Aug 4 at 12:45

Hi, I am a string theorist and a publicist.


May
25
answered Two introductory linear algebra problems
May
25
revised find skew lines on a cubic surface for a parametrization
added 168 characters in body
May
25
answered find skew lines on a cubic surface for a parametrization
May
24
comment How to understand and appreciate the prime number industry?
Lowest prime whose factors are not obvious? I thought that the factors of any prime $p$ are obvious, namely $1$ and $p$. ;-)
May
24
comment Fibration $v:S^1 \to \mathbb{R}P^1$ and a nontrivial element of $\pi_1(\mathbb{R}P^n,\ast)$
Unless there's some formal catch, I agree with @user8268. The circle $S^1$ is wrapped "twice" - from a point to the opposite point of the higher-dimensional sphere and back. This is a trivial path/submanifold both in homotopy and homology, isn't it? That's twice of the generator of the $Z_2$ group.
May
24
comment Linear Algebra Question
It was a pleasure, @MAxcoder. Thanks for your bounty. ;-)
May
24
comment AES Key Scheduler
Hi, look at en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
May
24
answered Simple (even toy) examples for uses of Ordinals?
May
24
comment Function growth comparison
Compare the $n$th root of these two functions. For the left one, it goes to $10/8$ because the difference between $n$, $n-2$, and $n+3$ becomes negligible when taking the roots, and for the right one, it goes to $\log(n)^5$. The latter is ultimately greater than $10/8$, so its $n$th power is also larger.
May
24
answered relations between root lattice and weight lattice
May
24
revised Finding Lagrange's form of the remainder with $a = \pi/2$ and $n\to\infty$
Dollar signs added around maths, nothing else
May
24
suggested suggested edit on Finding Lagrange's form of the remainder with $a = \pi/2$ and $n\to\infty$
May
24
revised A question about integral quadratic forms
Math put in dollar signs, no other edits
May
24
suggested suggested edit on A question about integral quadratic forms
May
23
comment Generalized “Worm on the rubber band ” problem
@Theo, this implicit isomorphism was just an expression of my lack of interest about the identity of the small guy. ;-) @Jean-Pierre, the result looks qualitatively OK for the situations I know - I just didn't know that you could integrate it in general. So I guess that for general functions $a,b$ it's wrong. Which $a,b$ are you substituting to the result if $a,b$ are whole functions of time? I don't really understand what you mean in that case.
May
23
comment Subtract gravity from 3D object in different orientations
Dear Steven, a detail, a typo: the operation is called "subtraction", not "substraction". ;-) Unfortunately, I don't understand what the question wants to say unless your desire is to subtract one 3-vector from another 3-vector.
May
23
answered Intersecting a polygon with four points
May
22
answered Laurent Series and annular regions
May
22
comment The graph of $x^{n}+y^{n}=r^{n}$ for sufficiently large $n$
In other words, for large even $n$, $x^n+y^n=1$ is essentially equivalent to $x\approx \pm 1$ or $y\approx \pm 1$ (with the other variable allowed to be essentially anything), which are the equations of the square. Note that neither $x$ nor $y$ can exceed one, so that's why you only get the 4 line segments.
May
22
comment The graph of $x^{n}+y^{n}=r^{n}$ for sufficiently large $n$
Let me say an answer using basic maths. Without a loss of generality, assume $r=1$; a different value of $r$ simply scales the picture. More importantly, If $n$ is very large and $x$ or $y$ are smaller than one, then $x^n$ and $y^n$ are much smaller than one - they're virtually zero, unless $x$ or $y$ are extremely close to one. For example, $0.9^{100}$ is still close to zero. So if $x^n+y^n=1$, then either $x$ or $y$ or both have to be extremely close to 1 from below so that the high power contributes almost one.