@Sanjana just in case you havent seen a bazillion versions of that integral, it is commonly appearing in intro to QFT as similar to a part of the correlation functions. This integral infamously is troublesome. It should be a Bessel K function, and you can reason things out from there. You can also show its asymptotic behaviour, approximate it in various ways, etc. If the argument in the paper is just nonsense, you might prefer to look at the rigorous derivations instead.
GUYS i think spinor might have had kittens im not sure. spinor was surrounded by 2 kittens and possibly more it was hard to see but i got a picture of one of them
3
they are a lot smaller than the picture makes them look. SO CUTE. the other one was moving too fast, but it was all orange, no white
@naturallyInconsistent Sorry for this late reply but yes, I have seen this integral. This isnt usually worked out in books, and that was the reason I found this QFT notes from a friend at a particular IIT.
Indeed from the last equation in the snapshot, they make a complex scaling of coordinates to convert that final integral into a "well known" integral form for a Bessel function.
So maybe the argument is wrong, but atleast the results are not...
You are getting this competely wrong. You have Equation (2.16) first and foremost. Then use Equation (3.70) twice to get Equation (3.114). It is clear that Equation (2.16) is in an earlier chapter and is not found by appealing to the later chapter. There must be some other way to get Equation (2.16)
@naturallyInconsistent Oh, I mispoke... I understood eqn. 2.16 fully. When I said "The 2nd term of 2.16 I can't understand at all", I meant that I couldn't understand the term coming in eqn 3.114 arising from the 2nd term in 2.16.
Nothing in particular. I have no idea, where to begin. For example, I feel that I have to modify $\vec{x'} \to \frac{a^2}{x'^2} \vec{x'}$ But I don't think it will bring any changes in the RHS of 3.70 apart from something in the spherical harmonics which I cannot figure out
I am seen people not considering QM/field theory/string theory to be particular "theories" because they deal with the formalism behind particular "theories"...A theory should be a model of some phenomena (like GR is a particular field theory and it is a model of gravitation)
Using that language, GR and QFT aren't even comparable...GR is a particular FT and QFT is just any field theory which is quantized. Why do people even compare them :)
No wonder introductory QFT is harder than introductory GR
@Sanjana Why do people say that there are only 4 fundamental forces? We don't know fully how to build the macroscopic world from the microscopic one. Are we sure that a new fundamental forces won't arise while attempting to describe some macroscopic aspect?
if you study a particular system in stat mech presumably it's governed by a Hamiltonian, which under whatever conditions can be transformed into a Lagrangian
at least how i have learned stat mech so far, the data is still coming from the microscopic model of the system. you just don't know what microstate it is in exactly
but the possibilities are just the state space as per usual
whether u are thinking about classical phase space or quantum Hilbert space
@RyderRude This video is a bit old. Nowadays some people say that AdS/CFT is a non-perturbative formulation of string theory. There are branes and other non-perturbative objects on the AdS side but because of the duality: all of these are encoded in the CFT Hilbert space ^_^
But yeah...not all of them agree, simply because afaik there's no full fledged "proof" of AdS/CFT
Yeah...Even I also don't think AdS/CFT should only be a guiding principle atmost. Some people are doing dS and celestial holography nowadays...but I think some day we must get rid of that background dependence if we are doing quantum gravity.
theres a guy @ IIT madras who does geometric quantisation, but is by and large a mathematician. I plan to approach him to give me a reading summer project, I was just wondering, this stuff is physics right?
@naturallyInconsistent well my intention was to just read something under the guidance of someone close to my house (which is close to IIT madras), and I was planning to read / do a project in math-. I was just scouting professors, and I came across this interesting profile
Technically, it is physics. It is, however, slightly more formalised than canonical quantisation, but not able to be a quantisation scheme that always works.
@naturallyInconsistent What is the difference between em waves of different mode, assuming polarization and intensity profile is the same, how do they differ if they are of different mode? What's visible or in any other form different ?
@nickbros123 That wont work. He needs to simply work out the algebra. All the prerequisites are already there for him to copy and just apply the algebra faithfully
@imbAF Have you never seen normal modes in classical mechanics?
Like first of all what is the criteria for modes? For example TEM, are classified as such because $\vec k$ is perpendicular to $\vec E$, while laguerre gaussian modes are classified as such because the spatial distribution of $\vec E$ or intensity profile (two different things) are circular, ring-like. So here you have two different criterias for the classification of what a mode is
@nickbros123 If you want to calculate polarization in crystals, you need to make dipoles: given an ion, there's an ambiguity in the choice of an oppositely charged ion, and hence an ambiguity in the overall polarization. Different choices give different values of polarization...
So in some sense, $\mathbf{P}, \mathbf{D}$ etc are not well defined, only changes in these quantities are "physical".
...why would they list both "unclassified" and "for official use only" at the top? Doesn't that mean that someone would need to strikethrough one of the two on every page. in every report?
If you ever read that bit about the CIA investigating psychic powers, how that went down apparently is that the psychics performed their demonstration in a hotel room?
Which seems a bit sloppy as far as an experiment goes
You might want a bit of a more neutral ground to avoid any legerdemain shenanigans
Unrelated, apparently. Part of MKUltra was testing LSD in "normal" settings.
"As the experimentation progressed, a point arrived where outsiders were drugged with no explanation whatsoever and surprise acid trips became something of an occupational hazard among CIA operatives."
