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11:10 AM
hey, small notation question... How would one say "x is small" - as in the "we linearize $f(a, x) = a \sin(x)$ with "x is small".
I can't state $x \approx 0$
 
$x \to 0$
any idea about how to enter two points $x,v$ in $\mathbb{R}^3$ and then a slider for $t$ in order to visualize $f(x+tv)$? In Geogebra, Wolframalpha, etc?
 
So saying "$f(a, x) = a \sin(x)$ with $x \to 0$ becomes $f(a, x) = a \cdot x$" is a correct way to notate this?
 
@paul23 No
 
I have come only till :
 
@paul23 There is actually no non-zero $x$ with $\sin(x) = x$.
 
11:21 AM
@TobiasKildetoft while true, when you introduce error margins one can say that. (Or well, the delta between those two functions is magnitudes less than the error margin).
 
@paul23 Then you should no longer write "="
 
= is only for when things are equal. =D
 
@JasperLoy there are Landau symbols, too :)
 
@Kirill = is also for smilies, like =D, lol.
 
@JasperLoy oh true, I have never thought about it
= is overloaded
 
11:32 AM
I am so happy I got 14 points for editing 7 posts yesterday.
 
I never find anything I can edit or answer..
 
any idea about how to make the value for $b$ visible?
 
@JasperLoy Hey! How are you doing? Glad to see you around. My projects depleted my energy lately. :-) It will be fine eventually. What are the news there?
 
@Waiting Not much news. Still trying to get better. But I am trying to go vegetarian from now.
 
11:41 AM
Is there a simple way to see whether or not a polynomial is positive on $[0,1]$?
 
run newton's method to find the zeroes
 
I guess one could check: its positive on $0,1$ and then see that all zeros are of even order
 
@JasperLoy That sounds interesting. I honestly never seriously thought of going vegetrian completely, not sure I'll survive. :P
 
@Waiting Well, some people go vegan, but I am only going vegetarian now. =P
 
@JasperLoy what do you study lately?
@JasperLoy :D
 
11:46 AM
@Waiting Nothing. Every day, I study only my mental problems.
 
@JasperLoy I always wonder what the "="sign symbols there. - The eyes? -- I've not seen anyone, ever, with vertical eyes. If yours look like that you might wish to see a doctor.
 
@paul23 Yes, I was also wondering about that actually, lol.
 
@JasperLoy You seems very fine to me. Never perceived you elsewhere. Sometimes I wonder if you're kidding with all the disease stuff. :P
 
@Waiting Yes, I seem fine but I am not fine. Anyway, I really like the pic I just took which I am using for my avatar. =P
 
@JasperLoy It's a nice pic.
 
11:49 AM
@Waiting You and robjohn don't talk much in this chat these days. I guess you are busy with real work, unlike me.
 
@JasperLoy I'm busy with my work but also with the stuff I told you privately. Yes robjohn seems busy too.
 
@Waiting I see. But what you told me is more or less over? I guess you are still dealing with it.
 
@JasperLoy Not over. Things are still up, trying to do everything to improve those things (if they can be improved somehow since it's the last stage)
 
@Waiting I can understand because there are things I have been dealing with for years and years.
 
@JasperLoy Yes. In a way it's at least good when things can be controlled in a way or other. In other cases, there is no way to deal with that kind of stuff (especially when advanced).
 
11:57 AM
@Waiting I still hope to do math if I can get well soon. I hope you will pursue your math studies too, because you are really good.
 
@JasperLoy You'll do it at some point. Thanks a lot. You've always looked to me more like a human than a machine which I appreciated a lot. It's not the kind of thing you see daily around.
This is to me a great sign of good health. @JasperLoy
 
Jan 5 '15 at 20:09, by user153330
user image
@Waiting See above! LOL.
 
@JasperLoy hehehehe
ROFL!!!
:-))))
 
It has your name there too.
 
@JasperLoy AWESOME!
:D
 
12:03 PM
That was 2 years ago in this room.
 
@JasperLoy Not sure at that time I saw it! Perhaps I wasn't around.
 
Given how because of completely unrelated reasons (trying to backup all my messages just in case maths chat imploded like Mos Eisley in the past) I actually crawl through everything back from 2013-2015 March
In other words, I have at least some idea on the history of users in that period
and their back stories
 
anyone can help with my question?
 
@Secret If I go through my things from 2013 to 2015, it would feel like a different person
 
For me, I am relatively constant, except for worldview paradigm shifts at 2004, 2011, 2015, 2016
 
12:10 PM
@Secret People say things, but how they really are it is hard to ever guess if they won't allow you to know them.
 
This is true
2004 = Scientism starts, imaginary friend become unecessary
2011 = Agnosticism starts, also starting to feel empathy related to people
2015 = Art exploration starts, more exposure to fine art
2016 = Esotericism starts, more exposure to the 3rd important branch of culture
 
@Secret do you have a religious background, if you want to share?
 
Nope, I don't believe in any religions, though because of my friends, I know a little bit of most common religions
 
then what does "imaginary friend" refer to...?
 
That was back in 2003 where social isolaton from my classmates is the strongest, thus based on a friend of mine who moved to another school. an imaginary friend is created
 
12:15 PM
I see
Then what does "agnosticism" refer to?
 
agnoticism is a belief where one is agnostic of the existence of deity. It is really the ultimate sitting on the fence belief system
Agnosticism is the view that the existence of God or the supernatural is unknown or unknowable. According to the philosopher William L. Rowe, "agnosticism is the view that human reason is incapable of providing sufficient rational grounds to justify either the belief that God exists or the belief that God does not exist". Agnosticism is a doctrine or set of tenets rather than a religion. English biologist Thomas Henry Huxley coined the word "agnostic" in 1869. Earlier thinkers, however, had written works that promoted agnostic points of view, such as Sanjaya Belatthaputta, a 5th-century BCE Indian...
 
@Secret so what was your position before 2011?
 
scientism
 
@Secret I mean, in terms of god
 
Atheist I think
 
12:20 PM
@Secret interesting
 
@Secret I believe in God, I'm sure about its existence, and I won't enter in any kind of debate, especially here.
 
That's fine to me
 
@Waiting then why did you mention it?
 
For me, the more interesting question is not whether he/she/it exists (cause numerous people have already ponder about that already), but how you can work with him just like most entities
 
@Secret most entities? such as?
 
12:23 PM
The supernatural
As evidenced from how my life is so far, it seems everything is mostly in alignment with my worldviews, thus I am not worried
 
@Secret what do you mean by the supernatural?
 
though the time when it will be shatter is approaching, and thus I need to be prepared for it
 
@LeakyNun secret liked to read my messages, maybe he also liked to know this relief. Doing mathematics and being a believer in God is perfectly fine.
 
@Waiting did he ever say otherwise?
 
The supernatural includes any entities that are not described in term of physics constituents such as quarks etc.

A lot of mathematicians believe in god if I recall, so are physicists
 
12:26 PM
quark... is... supernatural??
 
Ehhhhhhh
 
@LeakyNun since he mentioned he's an atheist, and knowing how atheists think in general about these matters, I clarified this point, from my view.
 
@Waiting if you don't mind, which God?
 
@LeakyNun should be pretty obvious as otherwise why the Integral Project will exists. Waiting and her Waiting Integrals (and ways in solving them) is one reason that might lead me to the closure of that integral question I have been asking since Grade 6 and her work with robjohn is one of the inspiration of that project
 
@LeakyNun The real God by which is possible now to have life and write to me (and address such a question).
 
12:27 PM
@Waiting Don't forgt this is 2017, and I have been agnostic since 2011
 
Free quarks aren't observable in nature directly. That doesn't make them supernatural
4
 
@Waiting which religion?
@Secret which question?
 
> The integral question: Why this substitution, how does it work in a mechsnistic level. What is the underlying symmetry that governs the integral operator?
Steamyroot said this question of mine is even more holy grail than the hodge conjecture
because not only I don't want to stop at compelx varieties, I want EVERY integral to be explainable
 
I think referring to the quark as metaphysical is more defensible
 
@Secret could you give us an example?
 
12:31 PM
guys, assume we are in an euclidean space
 
But then I'd consider a lot of physics to be 'metaphysics' in that sense.
 
and let $A_k$ a sequence of matrices such that $\lVert A_k \rVert = 1 + 2^{-k}$
Is there anything I can say about the norm of the matrix
$\left(\prod_{k=j+1}^{\infty} A_k - I\right) \prod_{k=0}^{j} A_k$?
 
Which norm is this?
 
norm 2
 
That second matrix---yikes
 
12:35 PM
to be specific $A_k = I + d_j2^{-j} J$
where $I$ is the identity
 
@user8469759 does norm mean determinant?
 
and $J = \begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix}$
no, norm means norm
 
like you square every entry and add them up and then square root?
 
no
not frobenious norm
 
never mind, I'm out
 
12:37 PM
If I could tell anything about the norm of $\left(\prod_{k=j+1}^{\infty} A_k - I\right)$
I would be happy
what norm is induced by the norm 2?
it should be equivalent to piking the eigen values
and taking max one in abs value
so like trivially norm I = 1
 
I misread the Wiki article
 
:39150353
Jun 26 at 16:41, by Secret
user image
 
The only thing anyway
I can notice
 
e.g. The integral $\int \sqrt{\sin x} dx$ requires choosing a correct substitution to simplify. (Of course that's not the only pathway, there are many others)
 
@Secret nice
 
12:39 PM
$\left(\prod_{k=j+1}^{\infty} A_k - I\right)$ doesn't have the identity matrix by construction
I'm not expecting to find the exact value, but at least an upper bound
(which I hope is less than 1)
 
but why is that, and does that have dependence on the nature of integrands, is what I am interested to know
 
user84215
I think that any proof of the existence of God that based on a scientific theory is not reliable since scientific theories are refutable.
 
I guess the thing I notice is that any product of such matrices is itself a linear combination of $I, J$
 
I think it's of the form I + c_j J
I think
 
-4
Q: Why is the slope not coinciding with the line?

AbhishekstudentSo, I went to desmos website and drew two graphs. One was the graph of $y=x$ and another was the graph of $y=1$. The graphs came out to be something like this But, shouldn't the line y=1 coincide with y=x, because, it's the equation of the slope of y=x. Where am I going wrong?

 
12:42 PM
Plausible. I'm not prepared to say either way
 
why am I being downvoted
it was a genuine question
 
Guys, there is no reason to downvote this question. It's an honest question that the OP is confused about. — 5xum 2 hours ago
 
Additionally, if M=aI+bJ then tr(M)=a tr(I)+b tr(J)=2a, and similarly tr(MJ)=2b
 
@aminliverpool I think we even need to define proof, existence, and God there very thoroughly before we can even ponder the question.
 
and for those who said "lack of resarch effort", this question is so concise that I cannot think of any better way to put more research effort
 
12:44 PM
Hi all, I was wondering whether anyone could help me with the GAP programming language?
 
would it be of any help if I tell is related to rotation somehow?
it's basically comes from my question this morning
 
@Secret Thanks for understanding
 
Pet peeve: people listening to music on their phone (without music) on the morning bus / light rail rides
 
@LeakyNun The truth doesn't need a religion to exist. People create religions.
 
In particular, does anyone know any command as to generate a particular group by sifting through conjugacy classes of that group?
 
12:45 PM
@Waiting do you ascribe to any religion then?
 
(This is on GAP).
 
@LeakyNun Born in christian religion.
 
@AlwaysNeedHelp But how would you get the conjugacy classes without having the group to start with?
 
Just because you enjoy listening to it doesn't mean we're interested in hearing it blasting
 
@Waiting now?
 
12:46 PM
ugh, this chat is really a black hole, I think I need to go offline in order to focus on my proposal writing...
 
@user8469759 just realized, you actually already have the eigenvectors of that matrix
 
@TobiasKildetoft:

I already have the group. Say let's take the group M_11 (the Mathieu Group) and we know that it can be generated by two elements (1,2,3,4,5,6,7,8,9,10,11) and (3,7,11,8)(4,10,5,6). However, I'm trying to see whether I can simply obtain a group G already established in GAP by another form of generation (by it's conjugacy classes).
 
@Semiclassical does that help?
 
@AlwaysNeedHelp By what conjugacy classes?
 
Every matrix you've stated is a linear combination of I and J. Consequently the eigenvectors are just those of J.
 
12:49 PM
@TobiasKildetoft Rational Conjugacy Classes. I.e I'm trying to find a way to generate M11 by a triple of conjugacy classes. Consider conjugacy classes C_1, C_2, C_3. I would like a way to write G = <g_1,g_2,g_3> where g_i is an element of C_i. (the conjugacy classes need not be distinct).
 
In particular, this means you can diagonalize these matrices simultaneously
 
@Semiclassical calm down...
I'm losing you already
sorry
 
@AlwaysNeedHelp So you are looking for how to make GAP generate a group given some elements? Or are you trying to look for elements with that property?
 
Well, J has two eigenvectors v1, v2 with eigenvalues +1 and -1.
 
yes
 
12:53 PM
@TobiasKildetoft. I'm interested in the elements that satisfy the conditions of generating G. In particular, I'm looking for particular conjugacy classes C_1, C_2, C_3 that will generate an already known group (that is well established).
 
So $A_k v_1 = (I+d_j 2^{-j}J)v_1=(1+d_j 2^{-j})v_1.$
 
@TobiasKildetoft So I'd like to find conjugacy classes C_1, C_2, C_3 s.t G = <g_1,g_2,g_3> with the g_i in each conjugacy class and g_1*g_2*g_3 = 1.
 
Hence v1 is also an eigenvectors of A_k
 
12:55 PM
@TobiasKildetoft Essentially if the thing could just spit out:

"The classes 2A, 4A, 11A satisfy the property." (Here 2A and the rest are given in ATLAS notation for conjugacy classes)
 
@AlwaysNeedHelp But then you are not really looking for conjugacy classes, but elements with a certain property and which happen to belong to different conjugacy classes
Ohh, you really want to conjugacy classes? But the property is the existence of elements in those
But the last condition means that you don't really need the third one
 
If $G,H$ are linear algebraic groups, does the product $G \times H := \bigl\{ \begin{pmatrix}g & 0 \\ 0 & h\end{pmatrix} : g \in G, h \in H\bigr\}$ carry the product topology of $G$ and $H$?
I'm asking because this would yield: $G,H$ connected $\implies G \times H$ connected
 
@abenthy Not as an algebraic group, no.
 
Oops, probably I should have k not j in the above
 
@Semiclassical I assume I can iterator the process for $\prod_{k=0}^{j} A_k v = $\prod_{k=0}^{j} (1 + d_k2^{-k}) v$
 
12:59 PM
Exactly so.
 
@TobiasKildetoft So what is the usual argument for why connectedness of $G$ and $H$ yields connectedness of $G \times H$?
 
@abenthy The product of varieties (or schemes) does not have the product topology but rather the topology arising from the definition of the product in the appropriate category
 
And it also works for the other matrix product
 
And therefore I can do the same thing with $\prod_{k=j+1}^{\infty} A_k - I$
 
@TobiasKildetoft Ah yes, this makes sense.
 
12:59 PM
So basically one eigenvalue is given by
 
@abenthy As far as I recall, the argument is essentially the same
 
$\left(\prod_{k=j+1}^{\infty}(1+d_k2^{-k}) - 1 \right)\prod_{k=0}^{j} ((1+d_k2^{-k}))$
 
@abenthy First, reduce to the affine case, then use that you know the coordinate algebra of a product
 
@TobiasKildetoft. If I did want to list all possible triples of generating elements g_1, g_2 and g_3 for the Mathieu Group M_11 satisfying the above properties would that be a feasible task on GAP?
@TobiasKildetoft Also, sorry, when you said the third condition is irrelevant, what were you referring to?
@TobiasKildetoft Thanks.
 
Right. Which you could multiply out to get (product over all k) -(product over k up to j)
Not sure that's useful, but there you are
 
1:02 PM
@AlwaysNeedHelp I did not say the condition was. The last condition (that the product of the three elements is the identity) means that the first two uniquely determine the last one
 
ok
but maybe
 
@TobiasKildetoft. Ah yes, I agree.
 
And also that adding the third one does not produce any extra elements
 
So that's one eigenvalue. What about the other?
 
I need to put -1
 
1:02 PM
Right.
 
@TobiasKildetoft I almost thought you said there was a way to remove a condition, my bad.
 
@AlwaysNeedHelp Not sure how feasible this would be in GAP. Might be too many elements to go through
 
so I assume there's a factor $(-1)^k$ somewhere
I've got the technique but now
I wonder the following
 
Yeah. Kinda annoying but there you are
 
the $d_k = {-1,1}$
I mean it's a sequence whose values can be -1 or 1
can this help somehow?
 
1:04 PM
Huh. So the choice of the eigenvalue of J essentially flips the signs of all the d_k
 
because, again, this tells me that the max eigenvalue of $A_k$ is $1 + 2^{-j}$
 
I feel like that should be useful, yeah.
 
please can you help me somehow ? I've been struggling for days
that's the idea anyway calling the messy matrix $H_j$, because it does depends on $j$ effectively
I have a transformation of the form
$e_j = H_j x$, where $x$ is given
what I wonder is whether or not $\lVert e_j \rVert$ is a decreasing sequence
my feeling is that it is
 
@TobiasKildetoft So, if I were to neglect finding the elements but rather the conjugacy classes, I presume that'd be feasible. I.e I wouldn't be interested in g_1, g_2, g_3 as elements but rather the existence of conjugacy classes such that elements from them generate the group G.
 
but I can't really manage to show why
I know that $e_j$ tends to 0
this implies the sequence of the norm tends to 0 as well
and therefore it is bounded
 
1:07 PM
@TobiasKildetoft If I'm not making sense, which tends to be the case far too often, I can show you what I mean. It's question 40 below. Rather than using tables, I'm wondering whether GAP could be used to do the whole process.

http://www.math.colostate.edu/~hulpke/lectures/666/hw10.pdf
 
@AlwaysNeedHelp Well, if you take a simple group that is easy as any non-trivial conjugacy class will generate the group
 
I was trying to express the bound using matrices norms but I can quite get to what I'm up to
 
@user8469759 We're probably out of the realm which I can say anything useful.
 
and I'm sure I'm sure I'm missing something
 
But what does $H_j$ have to do with $A_k$?
 
1:11 PM
@TobiasKildetoft I'd like to show that the particular group is rationally rigid in the sense that the conjugacy classes which to generate it obey particular rules (the product of three elements from the classes is identity and that there exist (not necessarily need to be explicity shown) three elements from the conjugacy classes that generate G.
@TobiasKildetoft

Also, the conjugacy classes would have to be rational in the sense that a conjugacy class C is rational if it contains every generator of <x> for x in C.
 
hi @mike
 
@AlwaysNeedHelp I am not sure what you mean by instead of using tables. As far as I can tell, you mainly need the table to see that those conjugacy classes are rational
 
@Semiclassical is taken from this question
0
Q: Residual analysis of the following recurrence

user8469759I'm trying to perform an analysis of a recursion. I'll provide a bit of background and then the actual question later. Let $\left\{ \omega_j \right\}_{j\in\mathbb{N}} = \left\{ \arctan \left(2^{-j}\right) \right\}_{j\in\mathbb{N}}$, let $\theta \in \left[-\sum_{j=0}^{+\infty} \omega_j, \sum_{j=...

It's a scaled version of a rotation transformation basically
 
@AlwaysNeedHelp That is not how rational is defined in the question you linked (I don't recall if it is equivalent)
 
Yikes.
 
1:12 PM
we can look the question in this way
suppose you want to rotate of an angle $\theta$, and you can express $\theta = \theta_0 + \theta_1 + ...$
you can build such sequence using the technique there
and that allows you to get
$x_{j+1} = R_{\theta_j} x_{j}$
I know this sequence of rotations converges, because the sequence $\theta_j$ converge, and the rotation is a continuos transformation
therefore I want to evaluate the error $e_j = x - x_{j}$
and the question is, is such error convergent?
sorry
is such error monotonically decreasing?
 
Yikes.
I don't know either way.
 
@TobiasKildetoft. There is a book by Michael J.Collins (Representation and Characters of finite groups) who on page 104 defines the rationality of a conjugacy class by the above.
@TobiasKildetoft I only just noticed the definition on the other document.
 
@AlwaysNeedHelp It does seem likely to be equivalent, but it also does happen that the same name is used for different things
@AlwaysNeedHelp Right, there we are math.stackexchange.com/questions/218302/…
 
 
1:18 PM
The condition about characters is way easier to check since we have the character table.
 
@TobiasKildetoft. Ah brilliant.
 
hi , if im doing cylindrical coordinates, doesnt $\theta \in [-\pi/2 , \pi / 2]$ ?
 
It can be done that way, sure.
Though, actually.
 
Does anybody know, how to enter the function $g(t) = \frac{f(x+tv)-f(x)}{t}$ in Geogebra, where $x,v \in \mathbb{R}^2, t \in \mathbb{R}$ free?
 
No, it'll be $[0,\pi]$.
 
1:20 PM
@Semiclassical why ?
 
View that situation from above.
 
the way i see it we go only untill we touch the y axis
right!
 
You see it?
 
yes yes , it was confusing for me :P
thanks
 
tbh I didn't see it right at first either.
key is that the axis on the right isn't the positive x-axis but the positive y-axis, etc.
 
1:22 PM
Alright.
 
@Secret If you're still here; Arguments for agnosticism ?
 
@TobiasKildetoft. If I'm not mistaken in GAP you can do a command such as RationalClasses(M_11) which gives a list of eight rational classes but in cycle notation.

If you define something such as t:= Charactertable(G) and do the ClassNames(t); you'll get the eight classes in ATLAS notation as 1A, 5A, 4A... e.t.c.
@TobiasKildetoft Do you know if from the latter part there's an easy way to find whether or not the group is rigid? I.e satisfies all those properties as stated above?
 
@Semiclassical i think the limits in cylindrical are $\theta \in [0,2\pi] , r \in [0,1] , z \in [r \ ^ 4 -1 , 4 - 4 r \ ^ 2 ]$
 
@Kirill use a slider for t?
 
@LeakyNun a christian now
 
1:34 PM
@Waiting any denomination?
 
@Semiclassical nvm, i think i did it right.
@Semiclassical i saw a solution that used $\theta \in [0, \pi /4]$ , and i missed that they multiplied it by 4 . they just divided it to 4 regions.
 
Yeah.
That strikes me as silly tbh
If it only had four-fold reflection symmetry, sure.
 
How is the G.F. determined?
 
But it's symmetric about arbitrary rotations. So one might as well just do it from 0 to 2pi and pull it out as an overall constant.
 
> Number of real integers in n-th generation of tree T(2i) defined as follows.
Let T* be the infinite tree with root 0 generated by these rules: if p is in T*, then p+1 is in T* and x*p is in T*. Let g(n) be the set of nodes in the n-th generation, so that g(0) = {0}, g(1) = {1}, g(2) = {2,x}, g(3) = {3,2x,x+1,x^2}, etc. Let T(r) be the tree obtained by substituting r for x.
For r = 2i, then g(3) = {3,2r,r+1, r^2}, in which the number of real integers is a(3) = 2.
 
1:38 PM
@Semiclassical exactly :P
 
@LeakyNun I've seen a discussion of that kind of construction, though I've not used it myself. Lemme find it.
 
Can $S^2\times S^2$ be embedded in $\Bbb R^5$?
 
@Semiclassical thanks
@AkivaWeinberger tries to imagine it
fails brutally
 
It's in Flajolet's book on Analytic Combinatorics, and happily he put a free pdf version on his website: algo.inria.fr/flajolet/Publications/book.pdf
Section I.5 (starting at the bottom of page 64) is on tree structures
 
@LeakyNun James 1:17, NIV: "Every good and perfect gift is from above, coming down from the Father of the heavenly lights, who does not change like shifting shadows."
 
1:42 PM
I know he discusses continued fractions forms of GFs in connection with those
 
@Waiting non-denominational Christian then?
 
Right, he returns to tree stuff in chapter 3.
In particular, if you look at equation (53) on page 195, he gives an example of such a continued fraction
Not as much there as I'd have hoped for, alas.
 
Well I do know that $S^2\times\Bbb R$ embeds in $\Bbb R^3$.
 
Continued fractions do show up in that text a few times, though.
 
@LeakyNun I got it I think
 
1:47 PM
How about this, if $\theta_j$ is a convergent sequence of monotonic decreasing angles defining $x_j = R_{\theta_j} x_0$ for some $x_0$
 
@AkivaWeinberger well congratulations
@Semiclassical I'm still loading the pdf
 
$S^2\times S^2$ embeds in $S^2\times\Bbb R^3$. Rebracket that as $(S^2\times\Bbb R)\times\Bbb R^2$, which embeds in $\Bbb R^3\times\Bbb R^2=\Bbb R^5$
 
defining $\theta = \lim_{j\to\infty} \theta_j$ and $x = R_{\theta} x_0$ is $\lVert x - x_{j} \rVert$ decreasing as well?
 
yup @Akiva
 
47
A: Do good math jokes exist?

Gil KalaiHere is a joke I invented (based on a famous one) and had mixed reaction. A young mathematician comes to present to a famous mathematician his conjecture and ideas. "You are absolutely wrong," the famous mathematician dismissed the young one. Next enters another young mathematician and presents ...

I don't get this
 
1:48 PM
yeah, it's big
 
@LeakyNun he is my Game Theory course teacher!
 
@LeakyNun The more generic entry, btw, is this one: oeis.org/A274142
Though it's not much clearer.
 
@Semiclassical I'm asking about how the g.f. is generated
from the problem itself
 
Yeah.
 
Chose the degree you love, or follow the safe predetermined path ?
 
2:01 PM
@LeakyNun Eastern orthodox church
 
@Waiting I see
thanks
 
@LeakyNun No problem.
 
@Semiclassical It finished loading
 
@LeakyNun did I say anything to indicate otherwise? I was just talking. It was a random example. -_-
 
@Typhon alright
 
2:15 PM
Wait, $\oint\bar z\ {\rm d}z$ is the area of the contour??
(I might be reading a complex analysis text)
Wait apparently it's $2i$ times the area
 
Hi, does anyone know of any way to calculate rigid triples of a given group - specifically the Mathieu Group via GAP (or another CAS).
 
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Q: Monotonic properties of rotations

user8469759Let $\theta \in [0,2\pi]$, and let $\theta_j$ a sequence such that $\forall j \; \theta_j \in [0,2\pi]$, $\theta_j \to \theta$ with the property $$ |\theta_j - \theta| \geq |\theta_{j+1} - \theta|. $$ Let $R_{\psi}$ the rotation matrix, counter clockwise, respect to $\psi$. By drawing something...

 
2:46 PM
@Blue That is a very beautiful palette of blue colours you have there.
 
Anonymous
@JasperLoy Hehe :P Thanks
 
Anonymous
BTW I had a question to ask. I can't understand what a "field" means. "In mathematics, a field is a set on which are defined addition, subtraction, multiplication, and division, which behave as they do when applied to rational and real numbers."....I can't understand what they mean by "behave as they do"! Any idea?
 
@Blue This is of course an informal sentence which I shall elaborate on now.
When one defines a field, one has to list the properties of these operations as well.
 
Anonymous
@JasperLoy Okay?
 
However, the sentence just wants to give you a rough idea for the moment.
And to give you that rough first step, it tells you that these operations behave very much like the usual addition, subtraction, multiplication, and division for the real numbers.
That answers your question.
As to the complete definition of a field, you can find that easily in many places, of course.
 
Anonymous
2:52 PM
@JasperLoy I couldn't understand what you're trying to say. Could you give me a couple of examples?
 
Anonymous
Anything on which addition, subtraction etc can be done is a field?
 
@Blue For example, one property of addition is that x+y = y+x.
@Blue Nope, the exact definition can be found in many places, like I said.
 
Anonymous
@JasperLoy Could you please give me a link to the exact definition?
 
Google it.
Seriously. It's a 30 second google search.
 
@Blue It seems you quote Wikipedia, which has the exact definition. You need to read more carefully, that is all.
 
Anonymous
2:55 PM
 
The article is very long, and you quoted only the first sentence.
Just continue reading it and you will know what you are asking.
 
Anonymous
Okay. Reading!
 
@Semiclassical I think Wikipedia is a good first sources of info for many things. I usually don't google, lol.
 
Yeah, and that's where I went first upon googling heh
 
Yes, indeed the first google hit is often Wikipedia, lol.
 

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