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09:01
@Committingtoachallenge I don't get your point.
It's a family discovered by me.
That doesn't mean you need a new integration method. They can be approached by combining more methods, it's hard to do all with one single bullet.
It's a pretty advanced integral, hard to touch (in any sense you want) ...
Well, in the end it's about an art, the art of successfully using your knowledge to get the correct result. It's not the stuff you meet in a top contest, but in some top research rather.
In 3 variables Mathematica doesn't get anything, only errors. In 2015 variables MMA is simply dying slowly.
What does MMA stand for @Chris'ssis?
@infinitesimal Mathematica
09:16
icic
You have 2,015 variables @Chris'ssis?
:D
@infinitesimal I can even have infinitely many :-)
@Chris'ssis This just seems like an integral over an open 2015-cube.
Aligned on $(0, \infty)$ in all dimensions.
Well, it did until you removed it.
It's obviously difficult for being a high-dimensional volume problem.
@Axoren ^^
That's just three dimensions.
What was that other thing you had?
@Axoren Yeap.
@Axoren The variant in 2015 variables on the intervals you mentioned above.
It's even nicer to consider $(-\infty, \infty)$ for the variant in 2 dimensions.
09:28
So, you want the integral of the following, right?

$$\idotsint_k_{k-\text{cube}_{0,\infty}} \left(\prod_{i=1}^k \frac{sin(x_i)}{x_i} \right) \frac{\sin\left(\sum_{i=1}^k x_i\right)}{\sum_{i=1}^k x_i}\ \prod_{i=1}^k dx_i$$
It might be easier to have it broken up like that.
@Axoren Yeap. But I don't need anything at the moment about that since I evaluated it. :-)
@Axoren Is it easier like that? hmmm
Ugh... The timer fucked me up
I can't edit it now.
@Axoren No worry. We know the integral.
$$\idotsint_{k-\text{cube}_{0,\infty}} \left(\prod_{i=1}^k \frac{sin(x_i)}{x_i} \right) \frac{\sin\left(\sum_{i=1}^k x_i\right)}{\sum_{i=1}^k x_i}\ \prod_{i=1}^k dx_i$$
The variant in 3 variables is pretty nice.
09:33
Why do you care?
Not as a "this is stupid"
It's actually interesting.
But it's curious.
What does it mean to you, this integral?
@Axoren A little masterpiece that I'm going to add to my book. :-)
That's terrifying. I'm glad I can't afford textbooks.
lol :-)
@Axoren Do you have any starting idea?
Do you think your book @Chris'ssis could or will be used as a textbook?
@Chris'ssis If you can separate the factor with the sums in it from the rest of the integral, maybe.
Its the most disgusting part of that integral.
Because it gets big in weird ways.
09:38
@infinitesimal As a textbook? Some problems in my book are insane, and in textbooks one don't usually meet such things.
anyone know about equilibrium solutions? I feel that the interwebz is playing a game on me
because seriously <0 is unstable, =0 is semistable, and >0 is stable
period
Like, chemicals that are in equilibrium and consist of a solute and a solvent?
That's definitely a chemistry question.
no consider this equation x(a^2-x^2)
equilibrium at x =0,a,-a
then to find stability I need to just pick a point inbetween those intervals
Oh, you mean the roots of the equation.
I have + - + - from those four intervals.
increasing, decreasing, increasing, decreasing
09:41
@infinitesimal On the other hand, I also have very nice limits that can be computed with the elementary tools in high school.
Let me show you one of them.
but everyone knows that when the result is negative it's unstable right!!! especially if <0 right?!
hate reading handouts on the internet with reverse definitions -_-
You should post a question on the Stack Exchange or email your professor.
why bother he doesn't reply back
Then contact the department with a complaint about your professor.
And ask them next class or during office hours.
ugh not the answer I need
especially when I did these problems more than once
09:43
Which subject is this?
Calculus?
@Axoren I didn't have the courage to do that neither in high school, nor in uni. :-)
differential equations x.x
I would have probably been smashed in the next days ...
So Paul's Online Notes had conflicting definitions with your professor?
@Chris'ssis perhaps a textbook for graduate students?
09:46
no ughhh
<- -> is unstable on a phase line
-> <- is stable
@infinitesimal Anyone with strong knowledge in calculus should be ready for almost everything there. I like very much doing integrals, series and limits although I have no math degree. It's addressed to people that love this area!
-> -> is semistable
the same effect happens when >0 stable, <0, unstable =0 semi-stable
how the heck can -1 <0 be stable? impossible.. unless it was a cobwebb but that wasn't mentioned today
I have already done that problem yes equilibrium is R = 0 and R = K, yes we can't take - lns
$\frac{dR}{dt}=-aRln\frac{R}{K}$\\

from K to infinity yes I have a negative result, and in the middle from 0 to K I have a positive result
the numbers and everything agree
but why the heck did he say -1<0 is stable unless he made a mistake to troll
sigh let R = 2K
$\frac{dR}{dt}=-a2Kln(2)$ should be negative
ln 2 is .69 x -2 = -1.38
My point is @Chris'ssis why don't you build-up the readers knowledge to the point where they can actually be able to do some of your "insane" questions and thus appreciate the beauty of math as you are experienced in?
$\frac{dR}{dt}=-a\frac{1}{2}ln\frac{1}{2}$
$\frac{dR}{dt}=-a\frac{1}{2}ln 1 - ln 2$
@infinitesimal You're starred! I have that in mind, I thought of that, but it's not that easy! :-) Your point is incredibly good, but I need to see how I can make it real.
09:56
@usukidoll Are you sure your professor meant that the differential was negative?
the result he got was negative... from K to infinity
I got negative too
but I thought anything < 0 means unstable
why did he say stable?
But it seems that stability has to do with the direction of the equation to the equilibrium points.
@infinitesimal On the other hand some told me it would be a great mistake to add such questions in my book. In the worst case to try to add some easier particular cases of the crazy generalizations.
So, if the differential is negative, and the equilibrium point is below the point at which you're measuring the differential.
should look like this on a phase line
<--- --->
if the result is negative, we are moving away from the equilibrium right?
@infinitesimal The risk is that some solutions might take more pages and then the solution is hard to follow. 1-2 pages solution is OK.
I agree @Chris'ssis there should be a balance.
I think if u have concentration u can follow I think
@Chris'ssis My point? I didn't have one. I was just asking why is your kind of integral new?
Working it out yourself might be a better idea
10:04
Not everybody has the ability to concentrate that long.
@Committingtoachallenge Because it's new. It's a new family. I asked about it some mathematicians and they told me they didn't see it before.
Ya what do u mean by a new integral
@Chris'ssis Like a never encountered before family of integrals?
@Committingtoachallenge Yes.
@Chris'ssis Example?
10:05
Wow great
@Committingtoachallenge It's newly discovered.
It looks demotivating to me :P
@Committingtoachallenge Why? Since you think like a computer you shouldn't be worried at all.
@Chris'ssis It just feels so disconnected from any motivation
10:09
Amazing.....u know if I right a book on new discovered problems on number theory and groups by me I will dedicate it to u @Chris'ssis coz u have given me a grewtidea
Write
@SayanChattopadhyay Thanks! :-)
@Chris'ssis What was the answer to that integral, did it converge?
@Committingtoachallenge Hard to believe? :-) Yes, $0$.
10:13
Hi @Chris'ssis @Committingtoachallenge I see you talked about me. =)
@ABeautifulMind Hello! You're everywhere! :D
@ABeautifulMind Rings a bell :)
@ABeautifulMind I was reading some of your messages from 2012, from deleted account
Finally submitted the review.
I can sleep.
@Axoren Nice!
@Axoren 5am now?
Yeah
Have a team meeting at 7pm, so instead of sleeping, I'm going to prepare stuff for it, skip today's class, and show up by 7pm prepared.
Sleeping now means I won't be prepared.
10:16
Tell me something @Chris'ssis if I use limit for eg limit as x tends to 3 for a polynomial
$$\3x^2+2x+4\$$ do I put x=3 in this or find any other value as in how do u find limits
I can sleep when I'm done.
Why do you have slashes after and then before your $$ @Sayan
@Committingtoachallenge I am very sad I am still so sick after so long. I am on the verge of breakdown. I need a miracle. I hope I find a way to make myself better soon.
@Axoren What Graduate roll are you? Masters, Honours, PHD - Or something else
PhD
10:18
@Axoren Very nice indeed!
@Axoren You do sound like a PhD student
But I made the mistake of taking the software engineering course instead of doing the thesis option, so I have to work with a team on a thing.
@ABeautifulMind Hopefully a miracle does happen
@Committingtoachallenge I think I do my best, but MDD, OCD and PTSD combined is a disaster.
@Committingtoachallenge I like Mariah Carey's song 'There can be miracles when you believe'.
@ABeautifulMind Definitely hard to work with such weight on your shoulders
Huy
Huy
@Axoren: Do you not like working with a team?
10:20
@ABeautifulMind I am listening to the amity affliction right now
@SayanChattopadhyay you mean $$\lim_{x\to 3} (3x^2+2x+4)$$?
@Huy I'd like to work with a team that isn't employed with opposite schedules.
Only recently have we managed to get a weekly meeting time organized.
Huy
Huy
@Axoren: That is rather unfortunate!
Yes ....@Chris'ssis
Give me a four bored homeless people any day.
Huy
Huy
10:21
@Axoren: You can work with me, I just finished resetting my work desk.
while working on metric spaces in rudins PMA
@SayanChattopadhyay $37$
@Huy I'm just doing it for the course right now. After this, I'm probably going to become a solo act.
Huy
Huy
@Chris'ssis: Did you do that without pen and paper?
@Huy lol :-)
Huy
Huy
10:22
@Axoren: Denied. :-(
U r putting the value as x=3
@SayanChattopadhyay Why do you think it would be anything else?
Then is there any occasion when u don't put the value x=to the value it tends to go to
@SayanChattopadhyay $\lim_{x \to 0} \frac{\sin(x)}{x}$
10:25
Then what should udo
There's something called El Hospital in Spanish.
@SayanChattopadhyay In the case of the seven known indeterminate forms you should be careful.
It either means you need a doctor, of there's some French guy who can fix it by taking derivatives.
@Axoren Isn't L'hop only for $\frac{\infty}{\infty}$ cases?
It's also for 0/0 cases, if I remember correctly.
10:27
Forms where u get0/0 are called indeterminate forms?
You can turn any $0/0$ case into an $\infty/\infty$
@Axoren It's been awhile, but I was pretty sure it doesn't include $\frac00$ case
@SayanChattopadhyay $\displaystyle \frac{\infty}{\infty}$ can be rewritten as $\displaystyle \frac{0}{0}$.
Looks like a squeeze theorem to me haha
$\frac 0 0 = \frac{1}{\frac{\frac 1 0}{\frac 1 0}} = \frac \infty \infty$
10:28
Or the unfortunate alternative name "Sandwich theorem"
Err...
That didn't look very rigorous haha
Ugh, the formatting is killing it
Essentially, you can just say, "we're working with the ratio of two 1/0s instead"
So I will use l hospitals rule
And then it's the same thing
10:29
Why are we treating not real terms like that
We were told to write quotes around anything like that which came up
Anyway I looked it up and you can, so it's fine. I'll recap that stuff tomorrow(since clearly I should)
bbl
Personally, I like adding an additional $s$ quantity when I'm dividing by 0.
It's a quantity that's the real successor to 0.
That's how I justify doing it.
0/0 = 1
How will I differentiate this......
$$(2x^2+4x+1)^i$$
Please, no one do that. It doesn't work.
Sorry if I m wrong with the LaTeX
How do I do it
@SayanChattopadhyay $i$ is constant.
How do you normally take a derivative of a function $f(g(x))$?
Consider $g(x) = 2x^2 + 4x + 1$ and $f(x) = x^i$.
10:38
But isn't i=sqrt-1
Doesn't matter, it's a constant.
So it's no different from $c$, $4$, or $e^{9001}$
I will do it by using $\frac f(a+h)-f(a)\frac h$
10:54
@Committingtoachallenge I need to confess you that after telling me yesterday you read 1,200 messages of mine I laught for one hour or so before being able to fall asleep. :-)
@Chris'ssis Really? He read 1200 messages? You laughed for 1 hour?
@Chris'ssis @Committingtoachallenge is committing to reading like 900 books
@ABeautifulMind Really! lol
@Axoren It's good reading books ... :-)
I'm just saying, if he's reading 900 books, he's already got the momentum to go through your entire chat history.
@ABeautifulMind Now he began the lecture on your texts as he said above. I hope you wrote well ... :-)
10:59
Oh my God...
There's a measure called the "Wiener Measure".
I just can't take myself seriously when I say "Classical Wiener Space"
@Chris'ssis I read 12,000 of your chat messages I said
@Committingtoachallenge Yeah, I know. That's simply too much.
@Chris'ssis Oh you said 1200 above haha
(a missing $0$)
11:17
@Chris'ssis Made it seem little of an undertaking though :P
@Committingtoachallenge But I had in mind the correct number. ;)
@Chris'ssis So I kept you up for an hour last night?
@Committingtoachallenge You might be a very good $007$ agent in my opinion! You enjoy stalking people! :-)
@Chris'ssis xD Perhaps
@Chris'ssis I do not :P
@Chris'ssis I have only tracked details of a few people in the past
@Committingtoachallenge I wonder if your girlfriend knows your passions, hobbies. :-)))
11:20
@Chris'ssis She knows I have been working on paranoia, anxiety and depression, so I suppose so haha
@Committingtoachallenge You have paranoia, anxiety and depression, really?
@Committingtoachallenge :-)))
@ABeautifulMind I had depression and anxiety diagnosed, but I am pretty good now in terms of depression(anxiety will ever remain, but isn't too bad), paranoia is undiagnosed and non-serious
@Committingtoachallenge I think the paranoia might just be anxiety.
@ABeautifulMind In the past I have had hallucinations, and my doctor thought it may be an early indicator of schizophrenia, but nothing came of it
11:22
@Committingtoachallenge I feel like saying some things to you now, I will send you an email in 10 min.
@ABeautifulMind Alright :)
@Committingtoachallenge OK, email sent.
11:38
@DisplayName Alchemy. Homeopathy. Sorcery. :P
@Committingtoachallenge I read your email, thanks.
@ABeautifulMind :)
@Axoren :P. I suppose I did miss history didn't I
@Committingtoachallenge I don't understand why I am still so sick after so many years, I don't get it. That makes me very sad.
@DisplayName I think Midwifing also used to be a science.
11:49
@ABeautifulMind Are you enjoying life even somewhat, despite the sickness?
But that's more Medical/Nursing/etc
@Axoren I don't think I will learn that, but I would put that under health I guess
@Committingtoachallenge I spend most days in great suffering. On some days I feel alright, but I never really became stable enough to start studying. I don't want to waste my life away like that, but I cannot help it.
@ABeautifulMind There is no advice I can give sadly. Only time can heal you my friend
@Committingtoachallenge I am going to eat with my mum now, see you.
11:52
@ABeautifulMind Chocolate helps. I have a minifridge stocked with stacks of Lindt bars.
Almost every problem except diabetes, chocolate helps.
@ABeautifulMind Ok, talk soon
Hi @BalarkaSen
welcome back
i was just passing by, having no intention to start chatting again ;) i was simply posting a message in the algebraic topology room.
11:58
icic
@BalarkaSen Oh you have given us up?
:p kind of
@BalarkaSen I did notice little of your presence, but I thought it just timing
@BalarkaSen Are we underproductive for your liking?
not particularly, but i have a tough year ahead of me this time.
keeping up with my school studies, mathematics outside of school and chatting all at the same time can be quite hard.
This is the blackhole of productivity.
12:01
@BalarkaSen Fair enough. We will miss your provocations to Ted
@Committingtoachallenge ah. if you do so again, just ping me.
i'll be happy to get free smacks.
I don't particularly approve of his style of "smacking."
better than bashing.
anyways, i'm off.
later pal
 
3 hours later…
15:15
hello everyone
anyone up?
Huy
Huy
Yes, I've been up for 11 hours.
Hello
I had a question..
...it's a basic modeling question
suppose I had a set of $(x_i, y_i)$ points
and I'd like to fight a "best fit" model for them
***find.
Huy
Huy
Ok.
Now, I know how to fit said points into a $y=mx+b$ model using the least squares regression
...but what if I just wanted to fit them into $y=mx$?
Would I simply substitute "0" for $b$ in the least squares matrix?
Huy
Huy
@daOnlyBG: Why would you do that?
15:21
if so, then the answer is pretty straightforward: $m= \frac{\sum_{i=1}^n y_i}{\sum_{i=1}^n x_i}$
Huy
Huy
I guess you could, but the regression will be a lot worse, no?
Of course it would
but my assignment is telling me to do so, and I can't argue against a book
Huy
Huy
Ok, I guess that would be the way to go.
mmk, thanks
Huy
Huy
Don't count on it thought, for I know very little about modelling.
15:22
oh. thanks anyway
Morning, @Huy
@daOnlyBG: out of curiousity, what are you modeling?
Huy
Huy
Morning again, @MikeMiller.
depending on the context, having the line pass through $(0,0)$ may reflect an aspect of the model
@MikeMiller: i'm trying to remember, what kind of math do you study
Topology, @Semiclassical, but what that entails means a wide range of things.
15:30
right.
any key topics within that subfield?
I (intend to) study smooth 4-manifold topology, where gauge theoretic/PDE constructions are important tools (as well as some serious homological algebra).
ahh. that explains why you'd want to learn some physics
Which is why I'm bumbling my way through a PDE course right now.
@Semiclassical the data of a spring's stretch
eh, I'd like to learn some physics because it seems like something worth knowing! not just because it would help me understand where certain ideas come from :)
15:34
heh, fair enough
@daOnlyBG: ahh. that's an example where, if you were doing it in the real world, you would likely not want to assume $F=kx$ is valid at $x=0$
i speak from experience on that point
lots of these ideas come from string theory, which is not particularly something I'm interested in
@MikeMiller: nod, can't say I am either
i get why people find it interesting, i'd just rather work on more accessible things
@daOnlyBG: by which i mean, when my intro physics students would take data for springs in lab, extrapolating their measurements all the way down to zero stretch with zero load isn't really valid
since at that point you can't talk about compressing the spring any further
(on the other hand, if you're modeling a certain physical interaction as a harmonic oscillator, then $F=k x$ being valid all the way down to zero may be perfectly reasonable. it's a context thing)
@Semiclassical I think there are interesting philosophical questions there (that are ignored by the falsifiability crowd): suppose you know that your model is insufficient at untestable scales. Is studying other models that modify this still physics, even if one can't test the difference between them?
it can be, i think, as long as you're honest about what you are and aren't doing
@Semiclassical thanks for the insight- I'm confident I follow your critique of the model
from a numerical perspective (i.e., void of any sensible application evaluation) the model is just not as accurate as using other models
but as I said, it's part of the math homework, so... bleh
15:41
that's true too
heh.
i think that's my conclusion too, @Semiclassical, but I probably would prefer if less time were spent on such things. on the other hand, I'm a math student, so...
the role of math/theoretical physics in that kind of scenario, though, is not so much to try to 'guess the answer' as to broaden the community's horizons of what options are out there
it's not about deducing the structure of the universe a priori, but extending one's horizons about what we can imagine as being relevant
plus, even if something is beyond your measurement capabilities, your choice/taste for theories will influence the kinds of questions you can ask and which you think are relevant to ask
for sure
the mathematics being developed is nontrivially applicable too; I heard from a friend of mine in solids that he uses some of the ideas they've seveloped for some of his (unrelated) computations
don't have more details than that
15:47
another point (which i'm not sure is quite the same as above): as much as physics may (rightly) try to avoid things which can't be made empirical, you have to accept some level of metaphysics in order to reason about the natural world at all.
and it's better to accept that, and try to be disciplined about it, rather than try to pretend otherwise
yeah, that's another point. the math may not change the meaning of the physics, but it can make deducing the physics much more obvious

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