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21:00
Guys, so Gauss’ theorem states that
$$
\int_V\nabla\cdot F\,dV=\int_S F\cdot\,dA.
$$
I have to verify the divergence theorem in the case where the surface is a spare of radius $R$ centered at the origin, and $F=(x,y,z)$.
Apparently the solution is $1+1+1=3$. How did they come up with that? Did they do something like this: $\int_V\frac{\partial F_x}{\partial x}dV=1$?
Suppose : $$P(E_1, E_2, E_3) =P({E_1}, \overline{E_2}, {E_3}) =P(\overline{E_1}, {E_2}, \overline{E_3})=1/8$$ , $$P(\overline{E_1}, {E_2}, {E_3}) =P(\overline{E_1}, \overline{E_2}, \overline{E_3}) = 1/4$$ and $$P(\overline{E_1}, \overline{E_2},{E_3}) = P({E_1}, {E_2}, \overline{E_3}) =0$$ @valentin
also, hi @Waiting
That's not the solution, @Sha. That's $\nabla\cdot F$.
@ShaVuklia Hi awesome @ShaVuklia. How are you doing today? :P
@Ted oh I see. I thought they already integrated, but they do that later on
@Waiting yea stressing a bit for my exams, but i'm good. You?
21:02
How do you read the Latex so easily?
Then $P(E_1) = P(E_2) = P(E_3) = 1/2$ thus $P(E_1, E_2, E_3) = P(E_1)P(E_2)P(E_3)$
However the events clearly are not independant
@valentin: They were not explicit, but that sentence should also say "for all $n\ge 1$"!
@copper.hat the sidebar has a link to a LaTeX renderer
@Ted Still, why do we have then that $\begin{aligned}\frac{\partial F_x}{\partial x}=1\end{aligned}$ ? Should I resort to spherical coordinates?
Also given enough time to start reading it right off
21:03
@ShaVuklia I'm sure you'll succeed! I'm in the middle of a battle with a problem. Apparently the problem has an advantage over me, but I won't give up easily. :P
@Daminark: Ta!
(i hope this isn't too confusing, it's far easier to see it with a table)
@Waiting haha alright:P hope you solve it
@Sha: Wake up. What's the partial derivative of $x$ with respect to $x$?
obviously 1, but we have the partial derivative of $F_x$
21:05
What do you think $F_x$ means?
(That's a counter example Ted didn't have off-hand)
@Ted the x-component of the position vector?
@ShaVuklia Maybe! Yeah, there is hope for doing that. :P
@Daminark: Ooops, too quick, what you do mean by the sidebar? I can't find any relevant link on te page I am looking at?
21:05
it must be a force
Ok done with chemistry. I have a few minutes before I want to go to bed.
@Vrouvrou Je t'ai dit ce que tu devais montrer
well, force field — in this case, the force at $(x,y,z)$ is the position vector $(x,y,z)$. But that's just a special example.
but they didn't specify a force?:( @Ted
ah
Sure they did.
21:06
Are you on a computer or phone? @copper.hat
so the sphere is a force field on its own?
desktop @Daminark
Let's see what math I can do with dope tracks bursting out loud.
No, no.
21:06
I get it
oh
@Astyx je n'ai pas compris l'histoire de la boule centré en $(x,y)$
yea no okay
but I get it
we have an entire field, but we consider the sphere
You typed ... $F=(x,y,z)$.
ooooohh!
You'll see some text at the right side of your screen
21:07
I did not realise its physical meaning
Well it'll say MathJax now that I think about it
Tu dois trouver un voisinnage de (x,y) se situant dans l'image réciproque de la boule centrée en d(x,y)
or any meaning, whatsoever
@Daminark: Possibly firefox on ubuntu doesn't cooperate :-(
ie une boule ouverte centrée en (x,y)
21:07
More pedantically, they should say $F(x,y,z)$ is the vector $(x,y,z)$, but no one bothers.
hahaha
bloody physicists
you can't live with them, nor without them
No, we mathematicians do this too.
i'll blame physicists whenever I can :P
21:08
It is understood that you're giving the value of $F$ at the point $(x,y,z)$.
Good life choice @Sha
@Daminark: I will try on my wife's macbook later...
hehe @Dami
thanks anyways, Ted!
Probably a good idea.
@Daminark: Oops again, just found it. Thanks. It is obvious once you see it :-).
21:09
@Balarka proves Hodge conjecture to the tune of... something
Beethoven's 9th symphony? :P
tbh hard to do anything with this shit. too good
@Daminark: That's pretty cool.
Mozart - Requiem in D minor -Dies irae
Haha, yeah
Mozart is good but I haven't listened to it systematically.
21:12
That piece is just wonders
I mostly listen to game soundtracks
Doom ost
@Astyx I could not understand what you are saying with your example but you use only E_1, E_2 and E_3 whereas the definition of interest uses E_i_1, E_i_2, etc. I want to know why goo.gl/B3Nu1u is doing that.
Haven't heard that, my favorite so far is Undertale
@Daminark you can try the thing i linked, but be sure to come back after you're teleported elsewhere
21:13
@valentin I'm giving an example of a distribution of probability with three events where we have $P(E_1,E_2,E_3) = P(E_1)P(E_2)P(E_3)$ but the three events are not independant
Will do :P
@Astyx On the note of classical music, Danse Macabre is interesting.
Saint Saëns is interresting generally
I'm liking this David Bowie
21:19
he's very likable
This album is one of my favorites, though less acclaimed
(It's a story, by the way. At the beginning of the new millenia (21st century), it speaks of a fictional apocalyptic world where the new fashion in art is an underground movement, of murder and making art out of corpses. and stuff happens)
I like Brahms a lot too, especially his first symphony
Ah I haven't listened to him
I like Bach, sort of classical europop :-)
21:25
You definitely should
Bach is fantastic, for sure.
Good part of Bach is good, true :p
(BWV 639 is my favorite, though I suppose everyone in this chat knows by now :P)
@BalarkaSen: I think it needs to be heard in a cathedral for full effect...
God I read that as Banach for a second
21:29
True, aren't a lot of Bach meant as cathedral prayer music?
Banach is okay too
functional analysis is messing you up
Yes it was what earned him his bread (kinda)
Lol yeah, and we're not even doing that now
I am always curious as to the evolutionary importance of music to humans, is it artifact or essence?
21:30
(Undertale ost looks interresting @Dami, thanks)
Lol I'd strongly recommend playing the game
It's real fun
@copper.hat I think those are not mutually exclusive, actually
@BalarkaSen: Yes, it really adds to the audio (cathedral).
I think abstract human constructs can easily turn into essence of life.
or thought even
If essence, then why (not expecting an answer, I have never got a satisfactory answer to this)? Clearly it is of huge importance, but why?
21:32
eg Maths
@Astyx I was thinking more like logic, but yeah
Well, mathematics, while it has poetry, clearly has evolutionary advantages (think page rank :-)).
I think it had evolutionary advantage before page rank lol
I think music is a viral meme :-).
Currently listed to some old '70s music by a group called Boney. M.
Daddy Cool
21:37
@Astyx: The 'uncensored' version youtube.com/watch?v=GiFelBDTBRs
Lol page rank was the first @Astyx what are you talking about?
Human existence as we know it now started with the web
hm, well, I'd actually want to ask what evolutionary advantage means to you. pure, selfless works of creation - however abstract and disjoint from reality - is useful to individual, to justify existence (which is an increasingly overwhelming question) perhaps. It's interesting to ask what the mass, in toto, use is.
Think of the advantages that $S^1$ conferred on mankind.
@Astyx: I think it is the beginning of the end :-).
@BalarkaSen: I presume that anything that persists has some long term survival advantage, otherwise it would have evolved out. No other meaning.
Me too.
21:42
The question is "Persist on which scale ?"
@Astyx: True, we may not last long :-).
not even 100 years according to Stephen Hawkings
prepare for doom and despair
I doubt humanity will be extinct in 100 years
@BalarkaSen: Things have to look dark when you spend most of your life looking at black holes...
(jk!)
21:47
@Astyx: If we can make it beyond current administration then I think following 96 years will be fine.
(That was not a right vs. left comment, and obviously a USA bias.)
I think that signals that it is time to do my chores :-)
Later folks, nice chatting!
Oh I think I'm all right in France :)
I wouldn't want to be in US right now but it's terrible in here too.
@Astyx: As of Sunday...
@BalarkaSen: Where?
India.
Sorry, just glanced at your profile.
I was in a place called Siliguri a long time ago. On the way back from Darjeeling.
21:52
Oh, very cool. I have been there.
though it's not where i live
I loved it. Kolkata too.
@Hippa o/
It's an okay city. I could live here.
(again unless I'm mistaken)
@Astyx o/
21:54
@BalarkaSen: For a tourist, it has a huge range of stuff.
Indeed, it does.
OK, I better go do the shopping, Mothers' Day in the USA tomorrow!
see ya
Bye !
See you!
22:01
I'll go too, see ya tomorrow probably !
Yeah maybe I'll head to bed too
22:13
Lol aight, see you guys around. I'll probably head to work
22:39
$\mathbb{P}=\begin{bmatrix}
0 & 0.8 & 0.2\\0.4 & 0 & 0.6\\0 & 0 & 1
\end{bmatrix}$, how to determine whether the classes are transient or recurrent
I got two classes, $\{0,1\},\{2\}$ if we let $S=\{0,1,2\}$.
Since $\{2\}$ is absorbing state, it must be recurrent. I am not sure class $\{0,1\}$.
23:20
@Simple The probability of remaining in $\{0,1\}$ seems to be less than 1, so I'd think it's a transient class.
since state 0 and 1 can go to state 2 and will stay at state 2 forever, class $\{0,1\}$ is transient
is that ok
Right. If they were trapped between each other (e.g. 0 goes to 1 with prob. 1, 1 goes to 0 with prob. 1), then both $0$ and $1$ would happen infinitely often and the class would be recurrent. But since they eventually escape, it's transient.
i.imgur.com/nIoVhX2.png I'm having trouble with this proof here. I let x be in D, and now I'm trying to show that $f:B(x,\epsilon) \to E^n$ is injective.
That is i'm trying find an $\epsilon >0$
this markov chain is not stationary since it is not irreducible

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