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16:03
9 mins ago, by John Rennie
@MichaelHarding hello?
uh what, now we are having the opposite on what I have been rambling about in the last 3 days...
echo echo echo
I am starting to believe h bar is weirder than quantum mechanics and GR combined
well, the hbar is currently full of people
so hbar != 0 and indeed hbar >>1
yeah. which sadly often means I need to go to sleep. Grr timezones...
therefore we're in a highly nonclassical regime and we should expect weirdness :P
16:06
> We expect the tunneling probability will not be adequately explained by the WKB semiclassical approximation
lol
strongly coupled
ok I am off for the night
try to make a higgs boson in the dynamics lol
wow circuits just hurt my brain
16:08
circuits are great man
as long as they involve linear elements at least
once you start including nonlinear stuff (e.g. a diode) then things sorta suck
my prof just started drawing a bunch of circuits and idk i guess ill just sit here and not understand
lol im so much worse at physics than i am at math rip
context?
i am just constantly a little confused in physics
16:12
yeah
it's hard to start midway in
yeah i kind of regret not trying to learn them seriously in tandem
Anonymous
@EricSilva Are you dealing with diodes and transistors?
idk what those are so i guess not but tbh i could be wrong
main thing is just this. with a resistor, the current through it is proportional to the voltage across it
Anonymous
Other than those diabolic stuff circuit analysis is pretty easy if you know the basic techniques :p
16:17
and similarly, the charge of a capacitor is proportional to the voltage across it
additionally, a resistor and a (textbook) capacitor are bidirectional: to reverse the current, you apply the same voltage in the opposite sense
a diode, though, responds differently to voltages applied in one direction vs. the other
Anonymous
Fourier and Laplace transforms are also pretty useful in complicated circuits
so it's easy to put current in one direction through a diode, but it won't allow the other
not without a lot more voltage than you'd expect, anyways
main thing is that the current os
Anonymous
@Semiclassical That's an underestimation considering the huge variety of differences that can occur in diodes. Mainly when you're dealing with the teeny-weeny diode currents
Anonymous
But in basic circuit classes they usually neglect the inner workings of the diode
16:20
right
Anonymous
And treat it as a black box
main point is that a diode isn't a linear circuit element
the response isn't proportional to the applied load
resistors/capacitors/inductors are, by contrast
which makes things easy since then the ODEs you get are linear systems with constant coefficients
@EricSilva a proper physicist doesn’t understand that either
Circuits are for engineers
ehh, depends on what one means by that
in terms of principles like energy conservation, charge conservation, etc
im neither a proper physicist nor am i an engineer
16:22
a physicist definitely knows what's up
but when it comes to how the individual elements work, then yeah
someone thought "ben sucks" was a bannable offense. sigh
@Semiclassical @Eric so I read that article
i saw
i think it's pretty stupid
reading it linearly put me to sleep, so I read it from bottom to top
and I couldn't see anything interesting it says
main point is just that it's a UChicago prof speaking in defense of Milo
yeah I got that
That explains a lot
16:24
she never really says anything interesting tbh she just gets mad and says words and none of it really amounts to anything
there was also a blog post which was a bit more colorful
@EricSilva perfect description of a physicist
A lot of Milo fans says "mumble mumble Milo points you out that everyone's touchy about religion mumble mumble" and I'm like, dude you know that the issue is that a major part of the current right-wing movement in US is about glorifying Christianity, right?
@BalarkaSen glorifying a specific version of Christianity at that
16:27
Catholicism, fair
@BalarkaSen feels bad when you’re an atheist republican so the other Republicans think you’re evil
@BalarkaSen what?
I didn't have catholicism in mind, no
You clearly do not understand American politics if you think Catholics are the problem.
16:28
the person who wrote the blog post he read is a staunch catholic
I do not think it's a problem
oh, fair
what Eric said
usually the touchstone is protestant evangelical Christianity
but as someone who grew up in a catholic house other christians fuckin hate catholics and i dont know enough about christianity to understand why (considering i am not and have never been one)
16:29
@Semiclassical Ah
something something the Pope = Illuminati?
idgi really
idk the protestant revolution was something about catholicism being evil and the pope being evil so youre probably right
so i guess all the branches that were born out of the protestant revolution carry within them this nascent hatred of catholicism which birthed them maybe
@EricSilva same
@EricSilva 500 Years ago...
i think it also goes to the extent for which protestant theology hinges upon an individual faith relationship with Christ
I’ve always thought Catholics were the chillest
16:32
I know about the catholics vs protestant thing but only superifically
i think there's also something about other christians thinking catholics like worship saints
It’s the crazy baptists you see walking around with bibles
and thus views an institution like the Catholic Church as irrelevant at best and idolatrous at worst
@0celo7 or Jehovah's Witnesses
I've seen them around campus
@Semiclassical don’t see those too much in the south
@0celo7 nah, Unitarians are the chillest
16:33
That’s not even a real thing
A religion has to be around for 500 years, otherwise it’s a fad
Like Scientology and Mormonism
If in the EM path integral, the $A^{\mu}$ are scalars, and correlation functions come from $\partial_{J_x} \partial_{J_y} Z(J) = <A(x)A(y)>$, what does $<0|T\{ A(x)A(y) \} |0>$ even mean
what about mormons
oh you beat me to it
@BalarkaSen i thought mormons were a thing from a musical
(that's a joke btw)
eh, Jehovah's Witnesses are more recent than Unitarianism
16:35
Are there any Unitarian operators
the only religion i take seriously is totemic religion
Tengriism is the one true religion
the joke from the simpsons i always liked was bart simpson and todd flanders playing a video game where you had to shoot bibles at people to make them christian
@Semiclassical it's not just a game that's how it works in real life
You can't even define $<0|T\{A(x)A(y)\}|0>$ if you start from the path integral, need to work with $<A(x)A(y)> := \int \mathcal{D}A A(x)A(y) e^{iS}$ right
16:37
Todd: Keep firing. Convert the heathens.
Bart: Got him!
Todd: No, you just winged him. Now he’s a Unitarian.
@bolbteppa whom are you talking to?
i only believe in the religion of Karl Marx
@0celo7 you, you read Zee
Das Kapital is my religious textbook
even though i have not read it
@BalarkaSen is the religion of marx that religion itself is a result of material conditions?
and capital accumulation
dude read kapital it's good lit
16:38
I have read the reader's digest
Communist Manifesto
read the eighteenth brumaire
I think @0celo7 doesn't believe in path integrls
What the hell, that is shocking
oh yeah you told me to read that before
literally every other sentence is top tier
16:39
tbh path integrals do seem like black magic to me
They mostly are
Some are well defined
But only some
what is a path integral
is it a functional over the loopspace or what
The physicist's take on Clarke's 3rd law
It's a integral over function spaces
what measure
16:42
Depends
Usually Gaussian measure
measures infinite dim spook me
Oh man, how do you even define a particle from a path integral perspective
You think you're doing great until you realize you were using canonical quantization implicitly half the time
You just have boundary condition measurements
ie you measure a particle at point x, you compute the probability of finding it in some open set at a later time
'A photon is just $J^{\nu}$ at $y'$ in $<A(x)A(y)> = \mathcal{Z}(0)^{-1} \dfrac{\delta }{i \delta J^{\rho}(x)} \dfrac{\delta }{i \delta J^{\sigma}(y)} \mathcal{M} \exp [ \frac{i}{2} \int \, d^4 x' \, d^4 y' \, J^{\mu}(x') \Delta^F_{\mu \nu}(x'-y')J^{\nu}(y') ]$ :p'
Same with fields except you use fields at a time t
16:49
The epistemology of QFT is fucked, honestly.
So there is none of this $A(x)|0>$ stuff apparently, or there is even though $A$ is a scalar, madness
although of course almost all QFT uses no boundary conditions
Except LFT
Seems like you can't ignore canonical quantization and just use path integrals I guess
Oh also there's that weird alternative
I just view the path integral as the Green function of the Schroedinger equation for now
What alternative
16:53
Which is half path integral half canonical
Hmm
What is that
Where you use $$\langle \Psi, \Phi \rangle = \int D\phi \Psi^* (\phi) \Phi(\phi)$$
Both of these agree for the vacuum since the vacuum is just 1
The Schroedinger functional formalism I think
I think that is basically just the Schroedinger equation where you throw away position vectors and then view the path integral as it's green function
'but, like, dude, the path integral is a completely independent perspective, man, where arrows rotate and then you describe the world'
Wavefunctional
Even Srednicki starts from canonical quantization and pulls the path integral out of nowhere only for correlation functions
17:00
the path integral is the Hilbert inner product
you can do correlation functions with canonical formalism but it is a huge bitch
Yeah it's really just not worth ignoring LSZ and path integrals, you get everything in 1 go so nice
I'm not 100% sure what the relation between path integral and wavefunctional formalism is
Since you have like $$\int \mathcal D\phi \Psi^*(\phi, t) \Phi(\phi, t) \approx \int^{\phi_f}_{\phi_i} \mathcal D \phi$$
there's something like that but I'm not sure how it relates exactly
Hatfield does it, treats the Schrodinger equation as an equation where the Hamiltonian is the e.g. KG Hamiltonian in terms of fields, $\int d^3 x \pi^2 + \dots$ and then just derives the Green function for Schroedinger with this insane Hamiltonian, in other words he actually derives the path integral without just saying what it is
the boundary conditions in the path integral formalism relates to the states in the wavefunctional one
Oh plenty of people derive the path integral
Yeah I remember him mentioning boundary conditions
17:06
I'm pretty sick of seeing the derivation really
It's not the $|q>$ derivation (I hate that one)
Finally! My internet connection was broken since Thursday, now it's finally working again
Hurray
I thought you died
17:07
My emotional reaction to that realization will be secret
(he cried a lot)
Tears of joy
@0celo7 If you dance on my grave I will come back to haunt you
btw, you know who has the actual path integral solution with boundaries?
Rovelli.
it's kind of a weird solution
@0celo7 Not Nice
17:12
$$\exp[\frac{i}{\hbar} \int \frac{d^3 k}{(2\pi)^3} \frac{\omega}{2\sin(\omega T)} ((\varphi_a^2(k) + \varphi_b^2(k)) \cos (\omega T) - 2 \bar \varphi_a(k) \varphi_b(k)) \prod_k [\sqrt{\frac{\omega}{2 \pi i \hbar \sin(\omega T)}}]$$
I have never even seen how you get the path integral for EM from the Schroedinger equation
@ACuriousMind also Not Nice
@BalarkaSen I might be a Nice ghost
Where $\phi_a$ and $\phi_b$ are the (fourier transform of) boundary conditions
threatening to come back to haunt people from the grave is not acceptable
17:12
@ACuriousMind A FP ghost
It's so confusing, the answer is so simple, just put $\mathcal{L}$ in the exponent, and remember quadratic Lagrangian means the derivation will work, so there...
@bolbteppa wot
@Slereah Ah, but then I'd decouple from all physical processes, which is boring :P
Where does the path integral come from, either you wave your hands and talk about phases like Peskin, or you derive it as the Green function to Schroedinger right
one thing I do wonder is if the same effect from non-relativistic path integrals affect the QFT ones
Is the class of functions non-differentiable anywhere
wrt $t$ only maybe?
I dunno
17:15
Zee does something interesting, discretizing the non-rel Lagrangian so it looks like the KG action, after you did the non-rel $|q>...$ path integral, which sort of covers the EM action too
Doesn't Feynmann Hibbs do the EM path integral?
Except weird
Where everything is Fourier transformed
I would be shocked if he does anything but derive it with phases and arrows then just saying you put $\mathcal{L}_{QED}$ in the exponent, will check sometime
(Side-note - what is the Schroedinger equation for the Double-Slit experiment? Apparently it doesn't exist)
@BalarkaSen flag it
@ACuriousMind you’d probably get grossed out if you follow me around everywhere
yeah 0celo7 has DiarreahG
@0celo7 I could haunt you part-time
Rearrange the order of the books on your shelves, change your passwords, that sort of thing
Leave physics "proofs" in the margins of your functional analysis texts
17:21
lmao
Rearranging the books is evil
I have major OCD when it comes to my bookshelf
@bolbteppa I think it's just free particle + an infinite potentials for the barrier
I would have thought so, apparently it's not, I have no idea how to model it and vague googling told me it doesn't exist and papers trying to model it and I gave up
@BalarkaSen my poop is in 3 states of matter
2
Sometimes 4 but only after lots of peppers
I hope it's not a Bose-Einstein condensate
it would crawl up the toilets
17:33
maybe it would
we need to get 0celo7 to poop at low temperature environment
for science
Anonymous
And then high temperature too
Anonymous
To ionize it to plasma
i have been telling him "go to gulag" for a long time
he thought i was doing it for political reasons
but its really because of science
I got the Friedlander btw
let's look up the integration by part
@BalarkaSen just out of curiousity, who is the Ben that you think sucks?
17:43
Shapiro
The cool kids philosopher
that was a good article
(@JohnRennie Do you know the mathjax code for single bond? )
@BalarkaSen you got suspended for saying Ben Shapiro sucks? Obviously there were a lot of republican supporters in the room at the time.
17:45
@JohnRennie Yup, seems so
Using - gives it as a superscript.
But alternatively it could just be a troll
like 70% of the flags in SE
@Abcd using the chemistry module for MathJax?
yes, I am typing a question on Chemistry.SE.
I don't think there is any support for chemical diagrams in regular MathJax
17:47
"To see how operators naturally emerge in a formalism defined entirely without operators",
hmm, Kaku seems to do it...
Not able to make single bond in CH2-OH......
@JohnRennie wait, now "-" works finally.
You need \bond
How to put a bracket below an atom?
Like a label...
No idea
There's a big MathJax help document somewhere ...
Hi, everybody
@JohnRennie fix my laptop plz.
17:51
@DanielSank what's up with it?
'the difference between Lagrangian and Hamiltonian formalisms is a Gaussian integral'
@0celo7 your poop is non-Newtonian. I wonder if Newton's poop was Newtonian ...
3
@JohnRennie It has broken Windows 8.
You know, that patch they released that makes the updater run all the time and hog the CPU.
Anonymous
Windows 8 is broken (by default) :p
17:55
@bolbteppa what is Gaussian integral? I also have read the term Gaussian transformation but don't know what it is.
6
Q: How are orbitals arranged in an atom?

DivyanshuI'm really confused about the ideas of orbitals, shell, subshell and most importantly how are they arranged in an atom? According to my knowledge orbitals are region having highest probability of finding electron.When I saw this video, I was more confused than ever. Lets say for a second that I ...

-1
Q: Structure of Atom?

DivyanshuI'm really confused about the ideas of orbitals, shell, subshell and most importantly how are they arranged in an atom? According to my knowledge orbitals are region having highest probability of finding electron.When I saw this video, I was more confused than ever. Lets say for a second that I ...

Look how the same question is received differently on two sites. Doesn't this clearly show how badly Chemistry.SE works?
Anonymous
@CaptainBohemian Why not just search on the net...
Anonymous
Gaussian integral is a pretty common integral
Yeah
@DanielSank if you wish to stay sane copy your data off, reformat and install a new squeaky clean version of Windows 10 then copy your data back. Your Windows key will cover you for Windows 10 so you don't need to pay anything. Even the install files can be downloaded from Microsoft.
17:57
@JohnRennie thanks.
There's a generic formula for gaussian integrals
@Blue do you mean that Gaussian distribution?
Like $$\int x^n e^{i(ax^2 + bx + c)}$$
@CaptainBohemian $\int_{-\infty}^{\infty} dx e^{-x^2} = \sqrt{\pi}$
If that's right
Anonymous
The Gaussian integral, also known as the Euler–Poisson integral, is the integral of the Gaussian function e−x2 over the entire real line. It is named after the German mathematician Carl Friedrich Gauss. The integral is: ∫ − ∞ ∞ e − x 2 d x = π ...
17:58
It's useful to have for path integrals
@DanielSank ask any of the numerous chat room members who I've talked through a Windows 10 installation. It's by far the best solution.
then I have learnt that in quantum mechanics book.
@blue back me up here!
\begin{equation}
\int_\infty^\infty e^{\alpha(ax^2 + bx)}\ dx = \sqrt{-\frac{\pi}{\alpha a}} e^{-\frac{\alpha b^2}{4 a}} \nonumber
\end{equation}

\begin{equation}
\int_\infty^\infty x\ e^{\alpha(ax^2 + bx)}\ dx = - \frac{ b}{4 a} \sqrt{-\frac{\alpha \pi}{ a}} e^{-\frac{\alpha b^2}{4 a}}\nonumber
\end{equation}

\begin{equation}
\int_\infty^\infty x^2 \ e^{\alpha(ax^2 + bx)}\ dx = (\frac{\alpha b^2}{4a^2} - \frac{1}{2a} )\sqrt{-\frac{\alpha \pi}{ a}} e^{-\frac{\alpha b^2}{4 a}}\nonumber
\end{equation}
Useful to have for path integrals
His exact quote:
"By performing the functional integral over $\mathcal{D}p$, we can go back and forth between the Lagrangian and Hamiltonian formalisms. In the path integral formalism, the relationship between the Lagrangian and the Hamiltonian formalism is no mystery, but simply the byproduct of performing an additional functional integration over momentum."
I wonder if the Legendre transform is legit related to this...
Anonymous
18:00
@JohnRennie Ah, yeah @DanielSank. I back up John as far as the recommendation to install Windows 10 goes. Dump Windows 8 XD
11
Q: We are discontinuing support for identification questions

Napoleon WilsonSince its very inception this site has struggled with the problem of identification questions and their controversial nature. Over the years these questions have become more and more of a quality and moderation issue and the community grew more and more weary of them and the work they generate as...

↑ well, this is new
@bolbteppa Well the Legendre transform is gonna be the classical limit I guess
'and now we perform the classical limit of a contact transformation on a jet bundle'
@EmilioPisanty there was some discussion on the SciFi SE about taking the SF film ID questions.
@JohnRennie this, no? yeah, that's where I saw it
don't ask me why I was there
18:02
I can almost deny the existence of the Heisenberg rep and re-define it in terms of path integrals...
Oh no
Not the jet bundle again
@EmilioPisanty we'll convert you to a SciFi nerd one day :-)
Well if you have path integrals, you don't need anything from the Heisenberg rep
At least one of our moderators has a high rep on the SF SE
Although it is still done a lot because path integrals and canonical quantization each have their own benefits
18:04
@JohnRennie unlikely
Hmm, but in Compton scattering you do $<p',k'|p,k> = <0|a(k')b(p')a^{\dagger}(k)b^{\dagger}(p)|0>$ and then use LSZ and pah integrals and you get the monster, I'm hoping to re-define fields via path integrals and then get LSZ from it just to see if you can do it
I was here mostly to complain aloud that it's wildly unfair that Stokes gets two concepts named "anti-Stokes"
You need those stupid $|p,k>$ vectors
A Stokes line is the radiation of particular wavelengths present in the line spectra associated with fluorescence and the Raman scattering. Stokes lines are of longer wavelength than that of the exciting radiation responsible for the fluorescence or Raman effect. Stokes lines are named after Sir George Gabriel Stokes. The energy of the scattered radiation is less than the incident radiation for the Stokes line, and the energy of the scattered radiation is more than the incident radiation for the anti-Stokes line. The energy increase or decrease from the excitation is related to the vibrational...
@EmilioPisanty In a quantum world all thing are possible, though you'd need to remain coherent for a while which might present some problems.
18:05
In complex analysis the Stokes phenomenon, discovered by G. G. Stokes (1847, 1858), is that the asymptotic behavior of functions can differ in different regions of the complex plane. These regions are bounded by Stokes line or anti-Stokes lines. == Stokes lines and anti-Stokes lines == Somewhat confusingly, mathematicians and physicists use the terms "Stokes line" and "anti-Stokes line" in opposite ways. The lines originally studied by Stokes are what some mathematicians call anti-Stokes lines and what physicists call Stokes lines. (These terms are also used in optics for the unrelated Stokes lines...
and skip all the canonical stuff
@bolbteppa you don't, but the alternative is worse
what did Stokes do to deserve that?
What's the alternative
The alternative is the weird ladder operators that depend on some test function
18:06
You mean the functional stuff
yeah
Hm, can you do asymptotic stuff purely with path integrals
I think Weinberg might talk about it?
In the appendix
not sure
does Weinberg write a book titled quantum field theory?
18:13
Weinberg wrote the bible, it's too hard
no that was Jesus
His approach is kind of amazing, 12 disciples, I mean cluster decomposition...
I asked a question in math chat and somone told me the answer is in Weinberg's quantum field theory, but I don't have that book.
I have it, what was the question
The hard cover of P&S is still one of the better covers ever, or Weinberg's cosmology
@EmilioPisanty ugh yeah
Makes Googling a real pain
18:16
the best cover is Spivak
Especially since there’s inconsistency in the literature about Stokes vs anti-Stokes rays
@Semiclassical not if you're doing Raman stuff
I have only seen old messy greying softcovers of Spivaks
> Somewhat confusingly, mathematicians and physicists use the terms "Stokes line" and "anti-Stokes line" in opposite ways. The lines originally studied by Stokes are what some mathematicians call anti-Stokes lines and what physicists call Stokes lines
thanks, Wikipedia, that clears it up completely.
Lol
“Somewhat confusingly”
18:19
I gave Stokes lines a go and ran away soon enough
Divergent series riemann surfaces scary scary
@bolbteppa yeah, I did that too some two-three years ago
The Bender book in the references is great, man I want to know this stuff
it's easier the second time around
whoa
the Airy Bi function has complex zeros?
bejeesus
@bolbteppa I don't know what the left derivative and right derivative in antibraket mean.
What does that mean, can you give an example
18:34
Doesn't Weinberg's quantum field theory define antibracket? It's in the Wikipedia article supermanifold en.wikipedia.org/wiki/Supermanifold
18:50
@0celo7 best notation for the product $TU = T^{abc...} U_{abc...}$?
Maybe just $\cdot$ I guess
The proof of the integral by part is much simpler than I thought

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