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12:15 AM
When will that rep recalc script reach the PSE?
 
12:55 AM
is there a difference between a velocity distribution and the product of a speed distribution and an angular one?
That is, is $F(\mathbf{v})$ different to $A(\theta)\cdot S(v)$? Where $F,A$ and $S$ are different distribution functions?
 
 
1 hour later…
2:10 AM
0
Q: Spike in my reputations

Ramanujan_πToday when I opened physics stack exchange chemistry I found that my reputation spiked up to 495 whereas yesterday it was around 335, for which I don't know how it happened? I just want to make sure if everything is OK as I don't know any reasons for this.

 
 
1 hour later…
3:20 AM
Oooo, we get to find out the real answer to my old question!
7
Q: What would it look like if rep for questions counted the same/more than answers?

tpg2114I suppose we can't change the way reputation works on just our site so eventually if this became a serious proposal change it would have to happen on the mother Meta. But before I go and get flamed there, I figured I'd start a discussion here. It seems that on our site in particular, we don't h...

 
 
1 hour later…
4:22 AM
I have a feeling antimatter, radiation, magnetic fields and electrical plasma are connected. Would I be right or would I be wrong?
 
 
2 hours later…
5:57 AM
@JohnRennie hi.
 
@EmilioPisanty I somehow felt it must get trouble. Despite numerous attempts to come up with two simple qm problems that are both analytically solvable and related by a perturbation that is accessible to p. t. theory I couldn't find one. I think its for a reason, since in that case you would be able to equate the infinite p. t. series with an (simple) term, which seems to be against all we know from number theory...
 
 
2 hours later…
7:50 AM
@Rudi_Birnbaum wait, what?
 
@EmilioPisanty I mean the QM electron on the ring problem with mag. field (but time-indep.).
 
8:47 AM
morning
@ScientistSmithYT I mean they can be, depending on the context?
But so can cats and antimatter
 
 
1 hour later…
10:09 AM
Cats tend to meow loudly when bombarded with antimatter
 
 
1 hour later…
11:20 AM
there are too many cats in physics and not enough dogs
 
12:09 PM
@Rudi_Birnbaum it's a separable problem. How could it 'get trouble'?
@Secret dogs are for engineering
(cf. e.g. Laika)
@Rudi_Birnbaum what does number theory have to do with anything?
> you would be able to equate the infinite p. t. series with an (simple) term
There's an entire branch of mathematics dedicated to doing that, it's called Analysis
It also goes by calculus
 
12:23 PM
 
lol right
 
12:47 PM
@EmilioPisanty I just know that you do not have recursion free algorithms for obtaining a general $n$th order perturbation correction term of say the energy. For that you have e.g. also Feynman diagrams. And this stuff is connected with modular forms.
@EmilioPisanty I make a claim: There is NO QM problem with a closed form solution (not like the Dirac-spike one with $\tan x=x$) that is a modification of another closed form solution problem were the two of them can be related by perturbation theory with a convergent perturbation series.
 
1:38 PM
@Rudi_Birnbaum as I understand it, the harmonic oscillator with a linear perturbation is a counterexample
It's tempting to dismiss that as "not a real problem", but then you have to produce an objective criterion for "real problem"
 
Can anyone suggest me a good book on quantum statistics for basics and ug level.
Or thermal and statistical physics.
 
1:58 PM
@EmilioPisanty @Ezze @ACuriousMind @AaronStevens
Hii.
 
@EmilioPisanty What is the infinite order PT correction and the analytic solution to this problem?
afiak both of them are inaccessible.
@EmilioPisanty mind I am not talking about a finite order PT solution at complete basis limit. I am talking about the infinte order P.T. series limit each order at complete basis limit.
 
2:18 PM
@yuvrajsingh Hello
 
Good evening.
@AaronStevens
 
2:30 PM
Good morning
 
Oo. Can you suggest a book on thermal and statistical physics. @AaronStevens
 
@yuvrajsingh I used Schroeder's Thermal physics in undergrad and really liked it
Other people use Kittel I believe
 
3:17 PM
A pet peeve of mine is when I type an answer to a question and then someone else posts an answer that does not provide any new information to what I already posted.
 
3:32 PM
Is it is easy to understand, for a person beginning from scratch. @AaronStevens
 
@yuvrajsingh Yes, Schroeder is a good intro book to thermal/statistical physics
You just need to know intro physics concepts
 
Why are TMT bars preferred over RCC structures?
 
OK. @AaronStevens
 
Some QM knowledge wouldn't hurt, but the necessary QM concepts are covered in the appendix I believe
I believe I took thermo and QM at the same time in undergrad, so I was able to handle thermo fine without a mastery of QM for sure
 
Actually some suggest me Berkley.
 
3:37 PM
I am not familiar with that
@user586228 Engineering might be a better place to ask that
 
OK, one last any book on vibration and waves.
Same ug level @AaronStevens
 
Ok @AaronStevens I have one question..May be this is not the correct chat.How much does 1500$ stipend amount to in Pullman for a PhD
I am from India so I am asking on an American context.
 
@yuvrajsingh At the UG level usually vibrations and waves are covered sufficiently in intro physics I would say. And then if other topics need more in-depth coverage then they are covered as needed
I other words, those topics come up in different contexts
I am not familiar with any intro books that are solely focused on vibrations and waves
That is not to say there are none
I just never looked into it or experienced it
@user586228 I am not sure what you mean
 
Like are u going to make any savings by getting 1500 dollars a month in Pullman Washington State as an unmarried male who hails from India?
 
OK, thanks I research on Google and I got this two book, have you heard about them
Vibration and wave by A. P french
 
3:43 PM
@user586228 I honestly have no idea. My first reaction is to say that that is not a lot of money...
 
And physics of vibrations by Hj pain.
@AaronStevens
 
@yuvrajsingh I haven't looked into or heard of books specifically about waves and vibrations
Sorry
 
OK, thanks for advice on thermal. Let me ask about this to other.
@ACuriousMind hi , can you help me.
 
4:04 PM
Why so silence here?
 
Just one of those days
 
those days
 
Haha
 
I always seen this man on meme and jokes , but I do not what he is.
@AbhasKumarSinha
 
4:11 PM
@yuvrajsingh DC Comics character, JOKER,
Do you know batman?
 
Yes.
 
he belongs to the same creation DC Comics...
 
Before your physics studies you need to watch The Dark Knight
 
Basically he was the enemy of Batman...
@AaronStevens those are not popular in India... We have different versions of it,
 
I always wanted to see the batman the dark night. But I haven t seen it.
 
4:12 PM
I didn't say anything about popularity
I just said you need to watch it
 
Do. You have a link.
I need hindi dubbed.
@AbhasKumarSinha
 
Google may help better...
@yuvrajsingh trailers are always there of the (recent JOKER Movie, different from Dark knight) - youtube.com/watch?v=zAGVQLHvwOY
 
I M really bad at this, because I do it want to open fake sites.
 
@yuvrajsingh everyone is bad at this, take a clean browser in incognito mode and try hours of pain... That's how you get it for free (illegal way) or pay to watch (easy, legal way)
@yuvrajsingh do you have amazon prime?
 
Naa a.
 
4:18 PM
@yuvrajsingh hotstar prenium?
 
Nothing.
 
@yuvrajsingh I'd suggest you not to go through online random websites, because they are not safe, a lot of malwares, so, wait for it on TV (UTV mostly gets them )
 
Actually there is no TV at IIT.
 
@yuvrajsingh use mobile apps, hotstar, they are free
 
Anyway, It, s OK, I am busy these days, so...... Leave it.
 
4:21 PM
@yuvrajsingh no TV in IIT? How the students survive?... :( that's unfair, I love Naruto and SpongeBob, I'll miss those :'(
 
Yes, it is the place to study, we are two roommates,
You will see SpongeBob on your partner.
 
@yuvrajsingh ah okay, then what you do whole day from getting bored?
 
@AbhasKumarSinha Use chat SE ;)
 
@AjayMishra hahaha :)
 
You are grad student, I guess?
 
4:26 PM
Use free WiFi.
 
@AjayMishra school
@yuvrajsingh ah that works :)
 
@yuvrajsingh Is there a direct connection to internet, or proxied?
@AbhasKumarSinha 12th?
 
Direct.
 
@yuvrajsingh Only IIT to give that, it seems.
 
4:28 PM
@Ajay Mishra where are you from
 
IIT KGP. :P
 
Which branch
 
Physics.
 
Engineering in physics.
5 year or 4 year.
 
No, BS + MS in Physics.
 
4:30 PM
Which year.
 
4th, haha.
 
Great.
 
Leave it. Are you participating in Inter IIT Tech meet, it is being held there.
 
So how fond the course, is it different from the BSc course offered by University
 
@yuvrajsingh First, sorry. A joke. Two colleges can't be compared, it is kinda like that of, as we have to take some breadth courses too.
@AbhasKumarSinha Which IIT you wish to go?
 
4:32 PM
No I am not, although I very much interested in sports.
 
Are you participating in Inter IIT sports?
 
Cool.
 
Are you.
 
let's talk in another chat room, this room is not meant for general chat.
 
4:35 PM
Come In physics for Indian exams.
 
@AjayMishra You don't go to IIT using wishes, you work years for that :)
 
5:25 PM
@Qmechanic are the rumours of a swag pack when you hit 100k true?
given that it's been a year since you hit the milestone
I don't really agree with the change in scoring, and it's not like I've been in a rush to get to 100k (or I wouldn't have slowed down my progress handing bounties out left and right =P), but it seems I've been put close to the line, and if there's swag to be got then I do want it =P
 
Hello @EmilioPisanty
 
@yuvrajsingh Please don't ping random users to answer your question, just post it - if someone comes along and wants to answer it, they will.
 
5:41 PM
1
A: Half-integer eigenvalues of orbital angular momentum

NessunDormaFrom $\mathbf{L}=\mathbf{Q}\times \mathbf{P}$ we have $L_z=Q_xP_y-Q_yP_x$. Then, introduce the following new operators (assuming units of $\hbar=1$): \begin{align} q_1=\frac{Q_x+P_y}{\sqrt{2}},\\ q_2=\frac{Q_x-P_y}{\sqrt{2}},\\ p_1=\frac{P_x-Q_y}{\sqrt{2}},\\ p_2=\frac{P_x+Q_y}{\sqrt{2}}. \end{al...

huh
that's a mighty interesting argument
go and show that answer some love, people
 
 
2 hours later…
7:23 PM
@EmilioPisanty See *Integer versus half-integer angular momentum*,
Ian R. Gatland, American Journal of Physics 74, 191 (2006); doi: 10.1119/1.2166372 for a more direct argument.
 
7:44 PM
@EmilioPisanty That's a well-known construction.
 
"Everything is a harmonic oscillator" strikes again!
 
 
2 hours later…
9:52 PM
@EmilioPisanty I solved it (particle on the ring + mag. field) and in deed its the first example I have found, that works like "analytical problem + perturbation = analytcal problem". The point is that only degenerate PT theory for one $\pm l$ state is required all other contributions are $=0$. And moreover the magnetic field breaks the $\pm l$ degeneracy. That was -- to me -- unexpected. The levels are $E_l = \frac{B^2 R_0^2}{4} - l B + \frac{l^2}{R_0^2} + V_0$.
Most surprising is that the perturbation does not change the states but only the levels, we then get linear terms in $l$.
$R_0$ is the radius of the ring, and atomic constants throughout. The state functions are $\psi = \frac{1}{\sqrt{2\pi}} \exp{i l \theta}$.
for $l \in \Bbb Z$.
Fun ting is that all integrals are like $\langle l | i B \partial_\theta | k\rangle = \pm \delta_{|k|,|l|}$ so thats why all order (deg.) PT series that contribute stop at the first term.
$E_l$ in the field free case ($B=0$) is exactly the levels of ther particle on the ring and first order PT yields the linear correction $-lB$ in its lower (of the two) eigenvalues form degenerate PT.
 
10:28 PM
Congratulation @Emilio Pisanty for 100k reputation!
2
@EmilioPisanty : And yes, there is a swag pack with T-shirt, cup, etc.
 
10:51 PM
@Qmechanic thanks =)
@Qmechanic nice =)
@DanielSank well, why wasn't it posted before, then?
 
11:16 PM
@EmilioPisanty Dunno.
I think that whole thing is in Sakurai.
Search "angular momentum oscillator" on the internet.
 

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