« first day (5117 days earlier)      last day (30 days later) » 

01:48
I'm working on a forced harmonic motion with damping lab i.e., using $$m\frac{d^2 x}{dt^2} = F_0 \sin(\omega t) - kx - R\frac{dx}{dt}$$ as the EoM
but I don't understand how the amplitude \[
A = \frac{F_0 / m}{\sqrt{(\omega_0^2 - \omega^2)^2 + 4\gamma^2 \omega^2}}
\] is only a function of $\omega_0$
or does that inherently assume the oscillator is in phase with the forcing function
like even if $\omega_0 = \omega$, we could have a $\pi$ phase shift so that the forcing function is opposing the displacement of the mass?
phase shift is $$\tan\phi = \frac{2\gamma\omega}{\omega^2-\omega_0^2}$$ with $\omega_0 = \sqrt{k/m}$ and $\gamma = R/2m.$ $\gamma$ is called a damping constant.
wait I think this is what my TA was talking about when he said this model/theory assumes/doesn't assume some initial conditions
when I asked about the time it takes to equilibrate when changing $\omega$
02:09
I think it has to do with transient motion dying out and reaching a steady-state solution that doesn't depend on any initial conditions. Could be wrong though
02:52
This happens for $\gamma>0$ though, so if a system is minimally damped (such as in the lab), we should be careful about the initial transient motion of the SHO before changing driving frequencies..
which we didn't do. Great
Whatever I don't think it matters that much. Even if the phase shift is such that the driving force is initially out of phase and destroys the energy in the system, it'll get back in phase naturally I think.
03:14
@Slereah it's unfortunate that I constantly feel embarrassed to be part of this country
like why are we way behind the rest of the world in so many things
not a good thing for a country with so much geopolitical influence. means the rest of the world feels the ramifications of whatever the hell's going on here
alright that's the most i'll vent on it here
03:32
Yeah, I've been fighting back an urge to blurt things out all day.
Apropos of nothing, what's a better name for a charge that's flickering in and out of existence, Marty McFly-on or, Ion McFly?
@Mr.Feynman you should write from your phone more often :P
@SirCumference are you talking about France or US? because Slereah is French and US isn't behind the world at all.
@Obliv This is correct
@LuckyChouhan by "we" I meant americans
The result is only applicable to the steady state. This is the same kind of shit that we do with Ohm's Law and so on; generations upon generations of students fail to notice that we are never talking about the transients and are instead asking students to focus first on the steady state, and then they would get themselves confused. It is another kind of Sissyphean hell just like ACM in hbar.
@LuckyChouhan it just feels like so many of our policies are antiquated by this point
healthcare is terrible, we're one of (if not the only) western country that has capital punishment, we're one of (if not the only) country that still uses an electoral college, etc
03:52
I don't think anywhere else has an electoral college. Most countries use Westminster-style legislatures.
also I came across this the other day, why are we one of only two western countries that legalizes mutilating our pets
Cropping is the removal of part or all of the external flaps of an animal's ear. The procedure sometimes involves bracing and taping the remainder of the ears to train them to point upright. Almost exclusively performed on dogs, it is an old practice that was once done for perceived health, practical or cosmetic reasons. Veterinary science states there is no medical or physical advantage to the animal from the procedure, leading to concerns of animal cruelty over performing unnecessary surgery on animals. In modern times, cropping is banned in many nations, but is still legal in a limited number...
@SillyGoose Miao miao had a row here in hbar with RR about it. In the end it was ACM and Slereah who came in and pointed out that the issue is down to definition of words. The issue is that GR tells us that acceleration has to be revisited whenever gravitation comes into the picture, and so a lot of us have a heightened sensitivity when people treat acceleration in SR.
it just feels like most of europe has been more progressive than us in a lot of areas
why can't we just look at what other countries do correctly
e.g. the nordic countries are consistently at the top of a bunch of quality of life lists, while we're usually somewhere in the upper middle. shouldn't we be taking notes on what they're doing?
this has also been a historical issue too. most western countries had abolished slavery before the US finally did it
it just feels like this country is so slow to make progress
@ACuriousMind I fully concur with you that photons are not localisable and all, but this "surface crossing function", can we use it to define the photon's wavefunction? If so, is it the Riemann–Silberstein vector? Want to hear your opinions on this matter.
American exceptionalism wrecks things in a lot of ways.
04:03
@qwerty Miao miao thinks it will be particularly helpful to consolidate a few facts. 1) Miao miao is with @Mr.Feynman on this issue: It is not just photons that are affected by the lack of position, it is all quantum stuff having the same sadness. It is just that if a NR limit of a QFT entity exists, then we can pretend to localise them.
@qwerty 2) This is actually more misleading than the fiction: Even though the classical Maxwellian solution corresponds to a coherent state and not to individual photons, the photon picture is extremely successful. Things that approximately behave as bosons tend to be treatable as single bosons doing this and that, and in the case of photons, it is even better than that, because photons do not interact with each other to the first approximation. As such, the fiction works in almost
every circumstance, and only when we explicitly need the anharmonics, e.g. SPDC, that we absolutely have to consider quantum corrections.
04:36
@naturallyInconsistent when you say "this" do you mean part of ACM's take or all of it?
 
2 hours later…
06:28
@ACuriousMind Newton just thought it was a rotating little corpuscule
From what I remember there's a few ways you can approximate EM fields into null paths, although that is classical physics
but you can at least try
@SirCumference I think you're ahead
Fascism is creeping everywhere
06:53
oh @SirCumference it seems like you don't like being an American (?) There are problems in every country, I used to think US as a wish-granting factory but as you said there are also problems, but US is one of the powerful nations, and as you belong to the academia and US has best universities and professor and research labs.
@LuckyChouhan It's not that I don't like being American, it's just that I'm vastly disappointed by how such a powerful nation is dropping the ball in so many areas
I went to a top 10 US uni and all I really got from it was gigantic tuition fees
@SirCumference but why should it bother us?
Should've gone to another country instead in hindsight
@LuckyChouhan Ethics?
@LuckyChouhan Frankly having a nation be this powerful is a big problem when its citizens are so polarized
It means other countries constantly have to deal with our fluctuating stances
Which in turn affects them
And if fascism succeeds in creeping up in our nation, it has international consequences as a result
@SirCumference that's not the problem only in the US everywhere people who wants power has an attitude "come what may", here in India political parties divide people by their cast and who does it better gets the seat.
06:57
@LuckyChouhan I'm not going to claim only the US has problems. It's just that many of the US' problems have already been solved in most western countries
2
or at the very least are far better off
Nobody's really solved healthcare yet, but the US manages to be one of the worst countries with regard to it
We seriously should be taking notes of what other countries do
@LuckyChouhan I have recently learned that Indians nowadays call caste abolition "woke"
Rammstein was right, we're truly all living in Amerika
@Slereah Honestly I'm just hoping this doesn't become a trend every century
@SirCumference you should look at european politics right now, it's not as impressive as you'd think
@Slereah Well I guess it's a "grass is always greener on the other side" situation
@SirCumference I don't know, but problem of one nation can't be solved by seeing how other nation(s) solved it. There are places where US is lacking but there are also places where no-nation is near to US. So...
@Slereah yeah, but it is still a giant issue on ground level,
07:02
Honestly if history is any indicator, fascism can show up anywhere
It's just scary that one country can have so much geopolitical power, since it's still possible for that to take root in it
I mean it's not like the US was particularly good before
that is true
It's only as an adult that I've realized how much our education systems sugarcoat the messed up things the US has done throughout history
that really only makes us liable to repeat them
@Slereah whenever I read or hear "European Politics" I remember only two people Emanual Macron and Giorgia Meloni, lol
Macron démission, as the French say
@SirCumference don't the give some native people wavier, I have heard of people who gets full wavier on their tuition fee.
07:07
@LuckyChouhan Only under exceptional circumstances
Vast majority of people are spending hundreds of thousands of dollars
Some unis offer scholarships to particularly promising applicants, but top American universities won't do that
They figure they're already enticing enough to anyone who applies
@Slereah why? he says, "I'm centralist." And very good friend of Indian government. Do your and people whom you know like him?
@LuckyChouhan did you not follow the politics
Last election the left wing won and he nominated a right wing prime minister, the losing party
Allying himself with the far right
Also Macron is "centrist" in the way of all centrists, he is a right wing person who does not wish to say it
His program is all about concessions to businesses and patriotism
@SirCumference One thing you don't understand is they charge fee because they provide students better facilities, professors, otherwise you can do your Bachelors and Masters in India with less than $1000 in many colleges but after doing that you won't get anything but just two certificates.
@LuckyChouhan Only thing I got from it was good research projects
The education was a joke. I ended up just learning from a textbook for all my classes
@Slereah oh, I didn't know this was the scenario, I follow some geo-politics but don't know so much about EU's internal politics.
@SirCumference hence,
07:13
@LuckyChouhan there are plenty of countries which do not have the problems the USA has; and the US has the money and resources to actually fix those problems
@LuckyChouhan That does not justify over $200,000 in costs imo
@SirCumference everyone learns from textbooks :')
It's not like many European countries don't have good universities with far better tuition
Macron is also very strongly in the MORE ORDER camp
I'm not quite sure what policy of his is meant to categorize him anywhere but the right wing
@SirCumference yeah, okay so what's the solution?
07:15
@LuckyChouhan I don't know if this is common in other countries, but American professors often demand you attend lectures (a "participation" part of your grade)
which just gets in the damn way if you learn from textbooks
Macron is a centrist in the typical way that he believes his ideas are not "ideology" but Being Reasonable, which is the most alarming thing you can hear from a politician
(anger's not directed to you btw, it's to my bad memories of that)
A sentence that emits Hitler particles
@SirCumference be a diplomat.
@LuckyChouhan Well from what I've heard European tuition is often free
Whatever they're doing sounds good
07:17
My university was about 400 bucks a year
@SirCumference no no, I understand. So after paying high-tuition fee, does every student gets job or something equivalent which will make the paying tuition fee worth?
Really for the price of American university, it would be cheaper for someone to study in Europe
@LuckyChouhan no! lol
Just spend a few years in sunny Europe
07:19
@LuckyChouhan not at all lol
I didn't get accepted into a grad school until my second year of attempt
and it's notoriously difficult to find work in a lot of fields these days
university was free in Aus for the previous generation, then politics happened
ultimately education can only get you so far. What really matters is prior work experience, which is a catch 22 of sorts
Extremely funny to hear the governments complain about the lack of scientific workers afterward rly
One thing clicked me suddenly is, US institutions charge too much fee because they're high in demand, @SirCumference
if you're looking for a good justification, there isn't one
07:21
@qwerty Was your tuition fee also high?
They're all dumbfounded that they can't find workers for quantum computing to work for their spook agencies
there's nothing better about US universities than European ones
@Slereah not as bad as the USA at all and not nearly as cheap as Slereah
many European universities like Oxford and Cambridge are just as well known as the very top unis here, if not more
Oh our universities are better, but our research budgets? Grim.
07:22
@qwerty sure, if they have billions of dollars to pay to Israel and Ukraine but, maybe it is not in their to-do list.
@LuckyChouhan In the modern day, what happens halfway across the world can still have significant ramifications to your own country
@LuckyChouhan it's a question of politics, which is what started this whole conversation in the first place ;p
@naturallyInconsistent that's precisely why I was objecting ACM's hate against photons :P
@LuckyChouhan 80% I'm here. I use my phone, unless I need to use many equations or write a question/answer
@Mr.Feynman editing a message on phone sucks so much
well, i probably ought to head to sleep now
'night
07:26
It sends it twice sometimes, unless you reload first
@SirCumference yeah me too
@Mr.Feynman .. you didn't sleep? it's nearly morning over there, right?
It's 8.27am. Basically dawn :P
I slept less than 7h
I have sore throat and my voice lowered, so I was testing it. It dropped about two-three semitones
Do you sing... opera??
No...?
But it would definitely be fun :D
07:41
oh, sorry. I was wondering how much of chat.stackexchange.com/transcript/message/63818807#63818807 was true :P
@qwerty I wish that was true though :P
08:25
> It’s therefore helpful to think of sets as like groups with no group structure, or metric spaces with no metric, etc
Gasp
What the hell is that page setting
it hurts my eyes
@naturallyInconsistent I can't currently find the links but there's an annoying debate in the literature about that - you can get a function that depends on position and does some of the things you want, but not all of them, and people are really split over whether or not that means you should call that function "the wavefunction"
user image
2
wise words
08:42
@Slereah everyone's preferred level of rigour is their own: anyone less is being sloppy and anyone more is being overly pedantic
All true, although I disagree that mathematicians are human beings
09:02
The Omen is a good film. it is about anti-christ coming to earth
@Slereah these inconsistencies r only nitpicks
09:24
but i get the point. just like physicist math is nitpicked, one can nitpick mathematician math too if one is precise enough
 
1 hour later…
10:38
@Slereah even DG is hell if you don't abuse notation a little :P
Although, I wouldn't call that an abuse of notation myself. It is understood that if you see $\mathbb{R}$ as a subset of $\mathbb{R}^2$ you mean of course the subset $\{(x,y)\in\mathbb{R}^2: y=0\}$ (Ora any of the other isomorphic sets in there, but this is the choice we make in this context, of course I'm pointing out the obvious now)
So that at the end of the day, $x$ is just a condensed notation for $(x,y)$. There is no possible ambiguity. Instead, I would call an abuse of notation e.g. calling the composite function with the same symbol, as we do a lot in physics
@Mr.Feynman ...but that's exactly what the text means by an abuse of notation - using notation in a way that is clear to everyone but not technically correct
Sure, I'm not saying the text is wrong. After all they are defining the concept of abuse of notation
I'm saying that my personal definition is not the same
I only call abuse of notation those things that are ambiguous, such as writing $g(y)=f(x(y))$ as $f(y)$, which physicists do a lot :P
Or also for Fourier transform, sometimes denoted with the same symbol as the function and a different name for the variable
I think your definition is just "abuses of notations are those inconsistencies that caught me off-guard before I realized what they were" :P
Rather that catching me off guard, those things that make my head spin if I try to handle them properly
Like, I can write the transformation law of any tensor instantly, abusing notation. If I try to stick to consistent notation with compositions, local representations and so on, it takes several minutes
And I end up having to abuse notation to write it well :P
I think the Kochen-Specker theorem's corner cases are coming to bite me in the ass
I'm trying to show an explicit example of a Bohr topos and like an idiot I picked $\mathbb{C}^2$
10:54
@ACuriousMind *clear to everyone except perhaps a few uninitiated students
And I'm starting to think that it's weird that no projector in there seems to be approximatable there, since either the projector is in there or they do not share an image at all
and then I think "Oh right this doesn't work in dimension 2"
Guess it's time to go with $\mathbb{C}^3$
is that the same $\mathbb{C}$ as $E=m\mathbb{C}^2$
Close
11:40
@qwerty he is cool Italian guy I guess,
@Mr.Feynman why once you said that "Never ask questions to Slereah?"
@LuckyChouhan One of the usual chat memes. Slereah is into pretty advanced and exotic stuff (at least for my meager understanding of math and physics), so most of the times you ask "what is that", you get a link which makes things worse :P
he's just expanding your horizons
I guess that I'm not at the level of understanding required yet :P
@Mr.Feynman yeah, that's pretty much true because he sends so many links here :D
He is a very powerful and fearful entity who exists out of space and time
and he's not a cartoon Frenchman
11:54
@Mr.Feynman is he your role model? :')
Mhhh, I'm not interested in the same kind of things he's interested in
To understand you must not-understand
ACM is my role model :P
never meet your heroes
@Slereah Hi, how you're this much smarter?
11:56
Much smarter than who
@qwerty but @Mr.Feynman has chances to meet him, but please do it soon... :P
huh?
@Slereah than me sir, how you study advanced physics along with philosophy and memes?
Pretty low bar, I'm a huge dumbass
I just read a lot of things
Would you suggest me something to read?
11:59
Any specific domain?
@Slereah yeah, in literature, philosophy or anything you like.
Well I'm currently reading Red Plenty :p
Not exactly a scientific book, except as far as data science and the eternal science of Marxism-Leninism go
Thank you for telling me about Red Plenty, I have found its website
> “There is no royal road to science, and only those who do not dread the fatiguing climb of its steep paths have a chance of gaining its luminous summits.” -Karl Marx
2
A wise man
12:29
@qwerty I don't have a clue of what he means
@ACuriousMind Hi there! If you do not mind my curiosity to ask, how is mass operator $M$^2 in string theory related to zero mode Virasoro $L_0$?
(Can we compute the mass spectrum by knowing conformal dimension, in other words?)
12:57
@Soldier What difficulty do you have in deducing this from the general relation between the Virasoro generators and the modes?
@ACuriousMind What a trivial question I asked, I apologize. Does this formula hold for WZW models too?
Say you know how primary field transforms under L0 (expressed in terms of affine currents). Then we know the mass spectrum from conformal dimension and excitation number
level*
13:21
I'm trying to figure out the various SUBLATIONS of the Bohr topos but since I'm using a toy model with $C^n$ I am fearing that results may be trivial
I think the resulting topoi may be discrete and therefore have nothing interesting wrt cohesion
But on the other hand I'm not looking forward to making the infinite dimensional version
All the Gelfand spaces are just boring discrete spaces of the eigenvalues of operators
I mean I can still do the ground opposition of unity, I guess : nothing is nothing and something is something
Big if true
@Mr.Feynman Lemme clarify when you said, "ACM is my role model :P" then @qwerty said "never meet your heroes", after that whatever I said means "you have chance to meet ACM (your role model) and you'd meet him soon." :D
Are defects in condensed matter treated by a stochastic schrodinger equation?
i read that defects are treated by introducing random (in space) perturbations to the hamiltonian. This sounds like introducing some noise, i.e. turning schrodinger into stochastic schrodinger
@SillyGoose I just asked this to ChatGPT see here
13:40
@LuckyChouhan Please don't put content from this chat into ChatGPT or other models without asking for permission first.
@ACuriousMind sure, unfortunately I can't delete it now :(
@LuckyChouhan are you trying to start a new trend that mimics the "Let Me Google That For You"?
also please don't reply with AI-generated content to questions people ask in this chat in general; they come here to interact with humans, not machines.
@think_meaning_builds Not at all, I get this thought many times that ChatGPT can answer most of the questions of Silly Goose clearly.
@LuckyChouhan Do you have the relevant expertise in condensed matter to judge whether ChatGPT's answer is correct?
13:44
Long time ago we had a huge argument over LMGTFY
because otherwise you're being extremely condescending to Silly Goose's questions here without having a leg to stand on
@ACuriousMind Please don't be eccentric on such a fragile issue.
Yes, it also involved condescending remarks
@LuckyChouhan I have no idea what you're trying to say.
Let Me chatGPT That For You
13:49
But I guess that's a "no, I cannot judge whether the answer is correct", which means you just posted computer-generated garbage you can't even vouch for, pretending that's somehow a worthwhile contribution to a conversation
@LuckyChouhan do you see the similarities
Classifying projections in $\mathbb{C}^2$ was easy enough but doing so in $L^2(\mathbb{R})$ is quite another issue I fear
Even the one-dimensional projections are nasty
They're classified by... some Eilenberg-MacLane space, maybe???
14:08
@qwerty the quotation with classical wave = coherent state. It is correct, but the "not particularly useful" is very very very wrong. It is most of the time more than justified to argue using individual photons. Only very rarely is there a problem
@Slereah By "classifying" you mean exhibit another "better understood" space the space of projections is isomorphic to in a suitable sense?
@ACuriousMind Well in the two dimensional case I can basically just label them by the 0 and 2 dimensional projections (both trivial) or 1 dimensional projections (labeled by the Riemann sphere)
And the abelian bon Neumann algebras are then just some assortment of those up to some rules
Easy enough to order
Yes (but also as you already mentioned the 2-dimensional Hilbert space is usually the worst possible example :P)
quite the worst in this case really
Well, less so than $\mathbb{C}^0$ and $\mathbb{C}^1$
But still a little
$\mathbb{C}^3$ is a bit better but it doesn't really exhibit continuous spectrum, so it's not as good as it could be
The 2d Hilbert space is the infamous counterexample to a bunch of theorems - I'm immediately reminded of Gleason's theorem which also only holds from 3 dimensions on upward
14:15
yeah, also Kochen-Specker
Basically all the good QM theorems that make QM special :p
I guess because fundamentally $2 + 2 = 2 \times 2$ [citation needed]
@Mr.Feynman literally said that am with ya on this
@ACuriousMind uugh, that is the kind of situation whereby it would be great if there is a listing of what the properties kept and lost are, so that people can judge for themselves!
What is even the complex projective space CP²
The Riemann splonrg?
@Slereah And $\mathbb C$ is usually treated as one-dimensional, whereas $\mathbb R^2$ is two-dimensional.
Whatever shape it is
"As a Riemannian manifold, the complex projective plane is a 4-dimensional manifold whose sectional curvature is quarter-pinched, but not strictly so."
Looks a bit trickier than a ball
Guess I can probably wing it and just use a few specific examples of ordered projections
Just need to find a few representative examples
14:38
@naturallyInconsistent meow had just woken
The opposite is true. Miao miao just got back from stupid work
Most stupid, because it was way past work time, and only just to deliver stuff.
And it was most annoying because people were having sexy time at miao miao place when miao miao received the order to go deliver shit
@LuckyChouhan I didn't know I would be meeting ACM soon. @ACuriousMind did you know that?
I didn't and the way it's phrased sounds vaguely ominous :P
ACM is nigh
2
Repent
14:42
You shall fulfill my destiny
brings out measuring cups
🍺🍹🍸🥃🍺🍺
🥛🚰☕🍵
14:56
> Men whose pleasures are so busy are not at leisure. For example, no one will be surprised that those occupied by useless literary studies work strenuously—and there is great band of these in Rome now too.
This sickness used to just afflict the Greeks, to discover the number of oars Odysseus possessed, whether the Iliad was written before the Odyssey, whether the poems belong to the same author, and other matters like this which, if you keep them to yourself, cannot please your private mind; but if you publish them, you seem less learned than annoying.
Even in antiquity people couldn't stand nerds
15:33
@naturallyInconsistent we have the legal right here to not answer after work hours now. I can't believe it was legal before.
miao miao was just doing a favour.
15:48
hope they appreciated it :)
@naturallyInconsistent Why is there always someone have a sexy time in your house? :P
16:25
@Mr.Feynman because miao miao iz funnnn, and the 2nd key is lent out for even more funnn
@qwerty Yes, definitely. Which is why miao miao was willing to pick that task up
17:23
Hi. An interesting tussle regarding the Doppler effect. I am still sure I am right but don't know if I convinced you. But that is not the point of this message.

I have written a book on cosmology, which I would dearly love to be read (even reviewed) by a competent cosmologist. Would you be willing to give it a go?
fqq
fqq
18:18
@ACuriousMind Good! Use your aggressive feelings, boy. Let the hate flow through you
18:44
@ACuriousMind They said the same thing of Jesus
We could push the joke further but we're getting on a dangerous territory, my friend
19:41
@JohnHobson Hi John :-)
You're wrong and you haven't convinced me but that isn't the point of the message :-)
I don't have time to read your book, sorry :-(
That honestly isn't me dissembling, my students are running me ragged right now!
I have been on a search for a solution to la places equation in cylindrical coordinates for the case of azimuthal symmetry, but I have not found anything. is there a reason for this?
@Mr.Feynman the real q is why isnt there always someone having sexy time in YOUR house
19:58
@Relativisticcucumber because people who enter this realm of perdition never get out
Chuck Norris is so calm and manly that he can carry out the Cavendish experiment with his own pair of b____
Ba-dum-tss.
20:19
I am wondering if I am overcomplicating doing an "integration by parts" for $\int d^4 x [\square' \Pi (x, x')] h(x')$
To properly integrate by parts, do we integrate by parts twice?
Since the first integration by parts will produce a "cross term" $2\partial_\mu f \partial^\mu h$ for example
ah yes i am silly that is precisely what should be done
A silly goose claiming to be silly
Honk
let’s see how long it takes me to also “hate qft” :~)
Reading through the classical field theory part of schwartz has been pleasant…
20:59
@SillyGoose that is the kind of hate that can only span from something you used to love
But it turned out everything was a lie, just a comfortable lie
 
1 hour later…
22:11
so i am reading through schwartz ch 3. is the idea just that (1) we imagine our field (classical or quantum) can be written in a power series of a coupling parameter $\phi(x) = \sum_{n=0}^\infty \lambda^n \phi^{(n)}(x)$, (2) we plug this into the appropriate equation of motion, e.g., $\square \phi - \lambda \phi^2 - J = 0$, (3) we match terms of the same order and truncate at some point to get $\phi \approx \phi^{(0)} + \lambda \phi^{(1)} + ...$
 
1 hour later…
23:39
@JohnRennie OK. Thanks

« first day (5117 days earlier)      last day (30 days later) »