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/phd/ - Physics

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25 Dec 2021Mathchan is launched into public
Catalog Archive

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  No. 49
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Do you look like a scientist?

File: WittenExam.png ( 1.24 MB , 1271x2938 , 1654802280975.png )

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  No. 6
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>>48
surely you can solve Witten's exam
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  No. 7 >>48
I believe the solution to 2. is
−λ16π2-\frac{\lambda}{16\pi^2}
where the Lagrangian for
ϕ4\phi^4
theory is
L=⋯+λ4!ϕ4+⋯\mathcal L=\cdots+\frac{\lambda}{4!}\phi^4+\cdots


3 (a) is a bit of a gift; it will just be a Gaussian integral which you can handle with Stirling's formula.

6 (a) is also a freebie; just look at the correlation function
⟨ϕ1(x)⋯ϕn(x)ϕ(x)⟩=0\langle\phi_1(x)\cdots\phi_n(x)\phi(x)\rangle=0
(because
ϕ(x)\phi(x)
annihilates the ground state) but you can also put this operator anywhere in the correlation function without changing its value so you're done.
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  No. 9 >>47 >>48
5 (a) is trivial.

k2ddk2B(k2,g,μ)=0k^2 \frac{d}{dk^2} B(k^2,g,\mu) = 0


this defines a beta function for us

the rest i.e. 5(b) is just solving the beta function at 1 or 2 loops. it's basically resummation.
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  No. 47
>>9
wow
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  No. 48
>>6
>>7
>>9
Does anyone actually understand all this or is it all fuzzy handwaving based on results no-one has actually stepped through in detail?

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  No. 46
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How do you draw translucent surfaces

Especially when they are stacked together, near each otherand causing near infinite reflections and refractions on their surface

Is there any diagram of sorts
Like how shadows and form is drawn and such

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  No. 21
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>>23 >>36 >>37 >>38
I am pretty sure this captcha is asking for the wrong answer.
6 posts and 1 image reply omitted. Click here to view.
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  No. 34
>>32
Yeah but you can't call people niggers or faggots on stackexchange, despite the site being full of niggers and faggots, so I find the captcha a reasonable entry fee.
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  No. 36
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  No. 37
>>21
What captcha
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  No. 38

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>>21
Awww fuck, the schizo is here. Arm your clonazepam guns anons.
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  No. 39
>>33
>When you want to talk about normie things, sure. When you want to speak truth to power it's not an option.
Kek. Most ppl here are probably midwit students, at least stack exchange/overflow has world-class researchers. Physforums is especially good.

File: classical_doppler_michelson_morley.pdf ( 946.16 KB , 1674110202548.pdf )

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  No. 35
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The classical emission model for light (source-independent, observer-dependent) satisfactorily explains the Michelson-Morley null result.

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  No. 18
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I once heard an anon on /sci/ say that most undergrad physics is irrelevant to modern physics and you should just get to QFT as fast as possible. Is this true?
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  No. 19
No, whoever said that is a brainlet and you should generally ignore whatever advice you get on that shithole site.
You should take your time to thoroughly understand each subject. None of it is beneath you. By understanding classical mechanics thoroughly, for example, you will have a far deeper understanding of how quantum mechanics and relativity work, for example (in fact almost every part of your physics education is improved by a stronger understanding of classical mechanics). If you rushed to QFT, you would have an extremely poor grasp of physics in general and an inferior understanding of QFT to boot.
All of these subjects are intertwined, so learn them all and take your time.
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  No. 31
>american education

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  No. 3
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For me, it's Fermi-Dirac
1eε/kBT+1\frac{1}{e^{{\varepsilon}/k_BT} + 1}


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  No. 5

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  No. 20

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I prefer the gaussian. It's simple, elegant, and surprisingly prevalent.

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