Apparently this artist (Salvatore Garau) sold an invisible sculpture for $18,000 a few years ago

His description of it was that it asserts "confirmation of its own nothingness"

> The vacuum is nothing more than a space full of energy, and even if we empty it and there is nothing left, according to the Heisenberg uncertainty principle, that nothing has a weight... Therefore, it has energy that is condensed and transformed into particles, that is, into us.

How do people pull this stuff off lol

Apparently other people have done it too. I guess you can make money by just spouting some quantum gibberish

physics.stackexchange.com/questions/129978 Can somebody confirm that if I have a $\delta(x-x_0)$ instead of $\delta(x)$ here, I just get an extra factor of $e^{i k x_0}$ in the final wavefunction?

@NairitSahoo why are you uncertain about this?

@NairitSahoo you get an extra $e^(-ik\x_0)$

I wonder why $\int_{-\infty}^{\infty}e^{ikx}\delta(x-x_0)dx$=$e^{ikx_0}$ works even though $e^{ikx}$ is not a proper test function

@SirCumference So he sold words for 18k ?what a world we live in lol

hi

@SillyGoose do u want to prove why the exterior derivative of a scalar gives a dual vector?

@naturallyInconsistent that message you sent yesterday got me thinking harder about the relation between the band index, the next BZs (2BZ, 3BZ) and the reciprocal vectors. As elemantary as it'a supposed to be I don't seem to be satisfied with any reference that I know, so do you know any be it notes, books or SE that breaks it down?

For example, in the case of the empty lattice, the free particle energy is $$\vec{p}=\vec{k}+\vec{G}\qquad \vec{k}\in\mathrm{1BZ}$$ and $\vec{G}$ is a reciprocal vector

So $\vec{k}$ selects the point of $\mathrm{1BZ}$, while $G$ selects the band (?)

@Arjun that, and he gave the buyer "a certificate of authenticity" to prove its existence lol

samuel-lereah.com/Commentary_on_nLab_s_Science_of_Logic.pdf

Attempting to decypher the nlab nonsense

@SirCumference I mean ofc people can do whatever they want with their money,but 18k would've fed a poor kid in somalia 3 meals a day for atleast half of his life lol

@Mr.Feynman Yes, the correct thing to study is the empty lattice. But I'm not sure why you say that textbooks don't cover it---those that do things slowly and draw out all the Fermi surface games from empty lattice upwards, should also cover this. It is just that professors usually aren't that patient. My NUS prof Sow Chorng Haur was a great prof who really cared about education and so he had some good notes about this. And magnetic breakdowns of the empty lattice. Very nice stuff.

@Mr.Feynman effectively, but it gets complicated when you are outside 1BZ

tada, gym time

do u think it's ok to quantise a theory using a parameter other than proper time as time

@naturallyInconsistent books do cover but I haven't been satisfied with the ones I've checked so far, so if you know any standard about (except Ashcroft&Mermin, which I've checked), I'll gladly check

@NairitSahoo remember that the translation operator defined as $$ T_bf(x) = f(x-b)$$ transforms, under Fourier Transform, in the folllowing way: $$ [\mathcal{F} T_b \mathcal{F}^{-1})](k) = e^{-i\mathcal{Q}b}, \text{ where } \mathcal{Q}f(x) := xf(x) $$

@SirCumference oh no he's Italian, thats some bad PR

@naturallyInconsistent Are u from Singapore?

@SirCumference afaik its just a way for rich people to move money around and stuff... like money laundering...

@Arjun yeppuu

@Mr.Feynman I havent seen anybody else put in that much effort. But surely there are some online resources for empty lattice? Even Kittel covered the empty lattice.

Do note that there are quite a lot of bad ideas out there. For example, the shape of the bandstructure seems to look like the quadratic bands are folded inwards. There is actually no folding whatsoever. It is entirely about rigid translations; goes to the other side of the BZ. But that kind of misleading is unavoidable.

okay so this is the diffeG path i am taking

manifold -> manifold morphisms -> curves & functions on manifolds -> tangent vectors -> tangent spaces -> (differential geometric) differential (what ACM calls $D$, i think)

so then to talk about cotangent vectors, I can, by definition of the differential say that if $f: M \to \mathbb{R}$, then $Df_p: T_pM \to T_{f(p)}\mathbb{R}$. Then, perhaps we can just say that $T_{f(p)}\mathbb{R} \cong \mathbb{R}$. Then, we have that $Df_p$ is precisely a linear functional over $T_pM$. This is just what a covector is.

However, how do I show that all linear functionals over $T_pM$ can be written in the form $Df_p$?

Would it just be to (1) observe that the dimension of $T_p^*M$ is the same as $T_pM$ (2) find a basis?

@SillyGoose Maybe the math chat can help you since we're very few here

no I checked even the math chat is empty :P

@SillyGoose these are the mathematical foundations for studying GR I suppose

I can only picture you studying QM and QFT lol

diffeg is also the foundations for classical field theory :D

(and qft)

and qm in the sense that diffe g is the foundations for lie theory

I looked up the QFT course's topics at my uni, they don't deal with any of these obv

good to know

i have only taken a very introductory qft course, so i'm not sure what's usually covered

but i think my interests in qft lie outside the usual content that is judged to matter

Ah ok so this is something you're purely doing on your own volition

yesh

i like the maths

yeah you're more of a mathematical physicist, we know that much at this point hahaha

You must be having fun :P I'm here stuck studying for my optics oral exam

the only good part was the one about density matrices (the two hours we spent on the topic), but that part is optional so they don't even ask about it :)

@naturallyInconsistent NUS Singapore is gon be my first preference for grad school any day! : )

I have a bunch of seniors from my clg doing their phd now in nus

@Arjun actually, dont come? Unless you are already nearby

@naturallyInconsistent why not?I'm from India don't know if that's nearby : )

Well, that is close enough. I didn't like it there though. Prof Sow was one of the bright spots

Oh!and are you a prof there by any chance?

no, im not there now

not even on that island

Oh!But I guess you're an academician now : )

no, im just a lowly researcher

So you're not affiliated to a university?

Tbh you seem to me more knowledgeable than most professors I've ever met..these profs have gotten their phds from top schools in the world nd work in top 1% institutes in India : )

@naturallyInconsistent both you n @ACuriousMind : )

@SillyGoose Just do (2); the exterior derivative on the coördinate functions clearly form a basis, and every form can be expressed in terms of them.

@Arjun im at a company now, yes.

@Arjun actually, that isn't the case. I know many profs who know way more than meow.

But each person has a specific niche to rabbit hole themselves into, and miao miao happened to have a rather wide set of rabbit holes

deeply so

@naturallyInconsistent I am uncertain about the sign. See Arjun says $e^(-ik\x_0)$. This should depend upon my convention of Fourier transform?

@NairitSahoo you're aware of the integral property of delta function acting on another smooth function right?

@Arjun yes

@NairitSahoo no; yes, signs are where you are most allowed to be uncertain about, but you should be able to get it with just one simple substitution. And yes, the conventions would impact this; but at the same time, you should be extremely familiar with the standard physics conventions---those are so important, that there exists no physics deviation from that convention!

hmm. Thanks

But anyway...... I have a new question: is there a way to derive the boundary conditions $n \cdot E_1-E_2= \sigma/ \varepsilon$ and $n \cdot B_1 - n \cdot B_2=0$, etc. in a Lorentz covariant way?

That is, you should not have needed to ask if you get $e^{\pm ikx_0}$ and instead only asked about the sign.

@NairitSahoo under what circumstance would you be needing to apply boundary conditions under Lorentz boosts?

@naturallyInconsistent (and @ACuriousMind ...) I suppose since we're on the topic if you'd feel comfortable sharing what motivated you to leave academia?

@naturallyInconsistent Idk. Let's consider this to be an academic exercise? I know EM is a Lorentz covariant theory, I just need a Lorentz covariant way to derive something which I derived in a non-covariant way!

@qwerty I'm not in academia. But my temperament is suitable for academia. I'm interested in the esoteric details that goes into making sure the physics we work with, will make modern society tick smoothly.

@NairitSahoo Then I'm going to have to ask you to go bother someone else. Nobody gets to waste my time on clearly useless pursuits without my own approval. That is, I'm perfectly fine wasting my time on useless pursuits in my own leisure, but that is the key: my own leisure.

Hi all. Im currently reading about the Pauli exclusion principle in my PChem textbook and im curious, is it necessarily the case that a multi electron wave function can be written as the product of single electron wave functions?

In the section on Hartree-Fock it makes that assumption but I’m not sure if thats part of that approximation or if its generally true

@NairitSahoo I meant you get $e^(ik(x-\x_0)$ in the final thing

@naturallyInconsistent does that mean you left cos applications in industry were more interesting...?

@Allie necessarily impossible. And in Hartree-Fock it is not a product, it is a Slater determinant; even one single Slater determinant is necessarily going to fail to capture some physics. There is no hope of using that to get the exact answer. However, it can get you results that are soooooo gooodd despite being wrong.

I see!

@qwerty a bit of both yes and no. My company is pushing on a research project, and so in a sense im doing academia outside academia.

@naturallyInconsistent Does the mathematically rigorous condensed matter physics have use in industry ?(I'm scared it's a no lol)

And the Hartree-Fock limit is the closest approximation possible by that method right?

@naturallyInconsistent I see, I wish you the best with it! or perhaps I should say lots of fish. :)

@Arjun how mathematically rigorous? Actually, quite a lot of those rigour came from fistfights. i.e. those were real careers at stake and plenty of money behind making sure that things are done correctly. But of course, you can find rigorous nonsense too

@Allie what limit? You can improve upon Hartree-Fock results by doing even more computation...

@qwerty yay, om nom nom

but it is sad; today at work miao miao went to ask a wise advisor for directions, and he said that the direction miao miao wanted to pursue is unlikely to be fruitful.

@naturallyInconsistent My friend sent me this yesterday..google.com/…

But then he was like, would you like to consider doing PhD...

@naturallyInconsistent More HF computations or other methods? From my understanding the book says that theres a limit to how good your approximation can get with HF, and after that people use perturbation or other methods

@Arjun those are all in the heavily used parts. My colleague had been banging his head on Vlasov equation for months. I mean, ever since he was hired.

The book calls it the “HF limit”

@naturallyInconsistent what does rigorous nonsense mean in this context?

@naturallyInconsistent Damn so that stuff is actually useful!?

@Allie post-Hartree-Fock. The issue is precisely as the book states: HF has a limit to goodness, so if you want to go better than that limit, you have to go beyond HF.

:66320516

Yup ok!

Thanks!!

I appreciate it 🩵

People made me believe all the mathematically rigorous stuff is useless irl and the hand wavy stuff gets you all the goodies: (

@naturallyInconsistent condolences!! but :O PhD? I would have thought you already did, but no?

@qwerty There is a tremendous chasm between theoretical physics and mathematical physics. Theoretical physics is busy finding new physics, using old maths to fit new phenomena, things of that vein, whereas mathematical physics often tries to rewrite the known physics theories in terms of rigorous maths. Sadly, even though we do get great insights into what known physics is really trying to say when they succeed, those rigorous formulations seem to never be applied.

@qwerty I ditched myow phd track to pursue this company

@Arjun all of those are heavily applied stuff. Boltzmann's equations, transport or not, are extremely annoying to solve. You can definitely feed your family on it, but always hungrily.

@naturallyInconsistent what kind of company you work for?

Also, note that chemistry department and condensed matter physics department is the richest bits of physics that you can get yourself into.

@Arjun research startup

@naturallyInconsistent Who do I bother? How to get your approval? When will you like to waste your time: I mean, when is your leisure time? I will come back when you have some leisure period to enjoy

@Arjun the downside is that if you do, you'll be no better than an engineer

thanks for sharing, @naturallyInconsistent. it's nice to hear about different life paths. tho idk if working for a research start up is less stressful than trying to make it through various postdocs / there are any vaguely in my field lol

I'm loving my work right now. That is not the case just a while ago in academia.

I'm still about equally unproductive, but hey, happyyyy

@Slereah LMAO we jokingly call profs who the above stuff engineers lol

@naturallyInconsistent Great to hear that meow is happy with his jobuu : )

@naturallyInconsistent that's soooo nice to hear. what's the main difference for you?

@Arjun and it would be time to go and partyyyyyyy soon miehehe

@qwerty each position comes with its own ups and downs. but it grinds against conscience when the entire research direction is purely scammy. If one cares a lot about morals, it may prove too much if one cannot at least prove to themselves that their work is trustworthy.

I mean, people may well not trust our research startup's output, but at least we arent in the business of lying to ourselves.

@naturallyInconsistent ahhhhhh. my PhD involved something like that. I managed to get out but not without a lot of damage.

I certainly do hope that the recent papers about taming quantum noise is actually good. That was the shitshow that miao miao is lucky to have exited very early on.

At least their direction isn't anywhere as doomed as mine

mine was obscure and new enough that nobody noticed or cared except me.

hey, that's most research. If you arent lying to yourself, you should be ok; unnoticed is the norm

dont be too hard on yourself

ahhh no I meant the corresponding shitshow that I escaped was luckily obscure

lol

and I managed to right it best I could in the end

apparently we all have lots of war stories

hahaha yes.

somehow I'm not completely jaded about science. I just don't know if I have it in me to go through the job insecurity and come up with research proposals and all that. and Im a little slow, it takes months to years for me to figure out things that it takes other people a few hours or days at most.

@JohnRennie Thanks ! I was bypassing the obvious fact. But the post you provided made it crystal clear

Science can be advanced by anybody.

Even the cold fusion nutjobs

sounds like ratatouille!

@qwerty I realized I didn't enjoy doing research. I like learning and I like teaching, but the research work you do as a theorist didn't appeal to me all that much. Also the precariousness of the non-tenure academic job market wasn't particularly inviting, either. And finally I had gotten a bit disillusionized with my specialty - QFT and string theory - but I could've switched topics, I guess.

@ACuriousMind does not care for research for he has already solved all problems

@Slereah hi

in canonical GR, we foliate spacetime into space and time

is the time here just a time-like parameter, or does it actually correspond to the time that a clock would measure, i.e. proper time?

it does not have to be proper time no

so it is more like just a parameter of a differential equation

but it is on a time-like axis

@Slereah it is possible for it to be proper time, given that proper time cannot be known in advance, i.e. before we solve for dynamics

Sure

how

Pick some initial timelike surface, apply the Hamiltonian flow to it, define your time function by the parameter of this hamiltonian

every simultaneous surface will be of proper time

but will this parameter correspond to what a clock would measure

Depends on the clock

oh

also it would only be proper time for those specific observers

Can't guarantee that to be true in general

for what observer? The one whose worldline is that axis?

Even in a boring case like SR you will have observers with different proper times than coordinate time

The same stays true in GR

yes. but i find it weird that we can know the proper time of even one observer in advance

cuz proper time is determined by the metric, which is dynamical

Can we

while in hamiltonian mech, time is like an external parameter

@Slereah but u said that this parameter corresponds to the proper time for that observer

yeah but you don't know in advance if someone is that observer!

yeah

there's nothing fundamentally different about the classical case anyway really, you can just do the same reasoning with Newton-Cartan spacetime

make sense

@Slereah oh

The big difference being that you have a preferred timelike vector field in that case

Well, a timelike one-form

i think maybe we r gauge fixing cuz there's gauge freedom in the metric, so that we have fixed the proper time for one observer in advance

is this correct

The fact that you can reduce your classical mechanics to some parametrized system by time is essentially that process, you select a preferred class of observer and then you quotient it out of the spacetime

@Slereah oh

also a thing you can do in GR if well behaved enough, but the choice of observers is less canonical

yes. e.g. time should not have a compact topology or anything wrird

if we assume topology is good, we can fix a time parameter and foliation before we solve for dynamics, right?

You basically just need to be able to define some appropriate fibration of time over spacetime

The ~synchronization bundle~

oh

@Slereah but how do u do that without knowing the metric first

maybe just assume that one exists

@RyderRude That's the theoretical case, practically things are different

If you want to do it properly, you can attempt to compute it using the time evolution and all

But in practice you typically just guess at it, if that's what you're doing

Almost every experimental condition you're basically in the Newtonian regime anyway

oh

if you want to see how people actually deal with ADM you can look at arxiv.org/pdf/gr-qc/0703035

typically there's a lot of assuming going on

i was thinking that, in general, one would first get a solution to EFE and only later be able to foliate spacetime into space and time

@Slereah thanks

The case you're describing is what he calls the geodesic slicing

oh

so they usually just guess, and not only they are able to guess a time-like foliation, they r also able to get the parameter to equal proper time in advance

i will have to read about it, so i can ask better questions

thanks

@Slereah en.m.wikipedia.org/wiki/Wheeler%E2%80%93DeWitt_equation this article says that, in canonical gravity, we trade the covariant metric for a space-only metric

Are we able to compute the proper time along an arbitrary worldline using this metric

You will typically use more the lapse function and such

oh

lapse function seems to be related to the time metric

Lapse function must be a dynamic entity then

They are

you don't just get rid of all the parts of the metric that aren't spacelike

Does the time given by the lapse function for the "special observer worldine" co-incide with the parameter of Hamiltonian mechanics

special observer worldine is the one we have used for foliation

It does if your Hamiltonian is just the geodesic spray

oh

i will have to read about it...

thanks

@RyderRude Even in classical mechanics, it may be useful to work with a time parameter that isn't the usual time, eg johncarlosbaez.wordpress.com/2015/03/17/…

is haag's theorem something that practicing qftheorists worry about

@SillyGoose theoretical physicists usually not, mathematical physicists yes :P

i see

what is the "wigner-weisskopf method" is it just a model of spontaneous emission of photons from an atom?

@ACuriousMind are you a theoretical physicist or a mathematical physicist :P

I worry about Haag's theorem :P

i just read a fiery answer by Lubos Motl

Oh no, Haag. Wrong moment to step in

I'm sure @ACuriousMind would prefer to talk about this haag

@ACuriousMind I need to link an SE answer in a (personal) document. Is there a possibility that the link or id of the answer will change in the future and my link will be dead?

Is there some sort of permalink?

@Mr.Feynman I don't think the SE link format has changed since the beginning, the link you get when you click "share" is as stable as it gets

since it contains the post ID you could even find the corresponding answer in the data dump with it even if the link stops working for some reason

Is the probability of SE dying during the rest of my lifespan concrete? :P

I'm a bit paranoid when doing bibliography because I always assume future me will me dumber than current me

@Mr.Feynman Which SE? Schrödinger's equation or Stack exchange? :D

@Mr.Feynman again, since SE is under a creative commons license, there are several data dumps (e.g. on the Internet Archive) that contain all posts up to a certain date and these are regularly updated; even the site going offline would not mean you can't find the post again from the id in the link

@ACuriousMind Oh, right. I didn't consider the archive

Yay

@Mr.Feynman There's also this dubious thingy that's apparently up to date to 6 years ago: physics.meta.stackexchange.com/questions/10581/…

Yeah, we've discussed that a couple of times in the chat :P

but the audacity never gets old, lol

@Arjun industry ==> make monet. doesnt matter if u make money rigorously or unrigorously

@PM2Ring JC Baez supremacy

@ACuriousMind not to mention people selling the SE books

@Slereah wth?

Lazy entrepeneurs make compilations of SE posts and sell them on Amazon

@ACuriousMind We can copyright strike them right?cuz I feel like they're making money off someone else's hardwork and scamming people for content that is freely available!

no, as long as they're correctly attributing the material the creative commons license allows this

But aren't they scamming people?

You can read all about it in this last link I pasted here

It's not a scam, nonetheless just from a moral standpoint I think it's indecent. Making money off of content that people voluntarily created and is free to read on the internet

Even if they adhere to the license etc.

@Arjun I'm not saying I'm a fan of what they do, but it's literally not a copyright violation

the license allows using the material for any commercial purpose as long as attribution is given

Hmm..but it feels so wrong lol

@naturallyInconsistent why do you say the entire research direction is scammy? Are they fudging results or something? Please elaborate cuz who knows might be useful in the future

If scam there is, it is perpetrated by SE for putting the site under this license

@Slereah But wouldn't it be a real problem to make it more restrictive? I mean if I'm working on some commercial project and I get some specific help in SE... I would need to think twice about whether I'm allowed to use it with a more restrictive license, won't I?

and in many cases that would defeat the whole purpose of SE

Well you can see the dilemma then!

It's just that the law can never cover and prevent people from doing every possible shitty thing lol

Although otoh, that argument doesn't apply to PSE

Why? some tech companies need physics help too

I guess one distinction the license can make, is between using the contents of an answer in some way vs. quoting an answer. Arguably, the latter can be made more restrictive

But I'm not a lawyer and I don't even know that license really very well

Is IT the only alternative for a theoretical physicist not willing to pursue an academic career?

@Mr.Feynman What's special about IT that relates to physicists?.. Some startups and tech companies need physicists (theoreticians or experimentalists). It's just that the numbers aren't very big compared to other positions I guess

I don't know, I don't even know why a company would choose a physicist over a pure programmer

But the number of physicists is more or less proportionally smaller too, so it balances out

@Mr.Feynman software or finance are the most common professions they end up in, yes

@Mr.Feynman One good reason can be, it is a position that has to do with a lot of numerical simulation. Many physicist can happen to have more experience with that than most programmers. Even when lacking the technical know how, they have the theoretical background to understand how to simulate a physical system

oh, IT includes software, I always forget that ;)

@Mr.Feynman there aren't enough "pure programmers", the tech industry grows faster than the programs that produce "pure" programmers

I guess where I live we have a weird nomenclature, IT stands for precisely all the tech guys that aren't programmers :D

A software career is not bad per se, but do companies usually provide formation? For example, the only programming language that I know is basic C. Not that I couldn't learn others but why would they choose someone who doesn't already know their languages 💀

@ACuriousMind sounds fair

also they do usually ask you about your tech skills, they don't just blindly hire physicists under the assumption they can do software engineering :P

@Mr.Feynman Are you considering leaving the academic path?

Damn it! Gotta learn some other language

@Amit Keeping options open. I mentioned that a couple of days ago. I've had a loooooong burnout

@Amit there are approximately zero jobs in "simulating physical systems" compared to everything else in the tech sector; they really don't hire STEM people for their STEM expertise, they hire STEM people because they have general problem solving skills and often come with programming knowledge

I'm using 0% of my physics knowledge in my job, and this is the norm among people who studied physics but now work in tech

@Mr.Feynman I see but like, are you in the middle of a PhD or something like that , that you're considering to give up on?

@ACuriousMind 100% agree that a Physics major that can also program in language X is way more attractive to any reasonable tech firm than someone who can just program in the same language X. Those companies know that a Physics degree is a stamp that indeed says "problem solver"

I guess my answer to Mr.Feynman's question was assuming that he also wants to apply his actual physics skills & knowledge in some manner in said job

@Amit no no, just at the end of my master's

@Mr.Feynman If you have a strong grasp of C that's an amazing starting point to learn OOP languages like C++, Java, C# and probably several others languages that basically expand on the C syntax albeit with varying degrees of (at times, crucial) alterations of syntax. Anyway the major alteration is conceptual in understanding the "Object oriented" business, but since that was invented to make programming ultimately easier, it shouldn't be difficult

I guess nothing is difficult per se, just that someone who already knows is more desirable :P

ofc. Question is also, whether you like this stuff or not. Liking in this context means probably sitting every day for at least a good 5-6 hours and writing code with this stuff ;)

or debugging it...

Man, am I living in a time loop?

Anyway, if you're at the end of MSc it definitely makes sense to weigh the options

:)

@Amit the hBar has PBC

:O

@PM2Ring interesting

i would say other parameters are fine even in QM, as long as u know how to convert between them and time

but in quantum gravity, a strange problem arises, as the actual time becomes quantum mechanical, while the parameter time stays a parameter

so the theory becomes non predictive, as the parameter time can't be measured in experiments

in Wheeler Dewitt equation, this problem doesn't arise. But this theory does not have parameter time (i think), and the actual time is quantum mechanical

@RyderRude there's this new interesting (in my mind) question, when I read it I thought the linked article is the type of thing that's exactly up your street ;)

@Amit thanks

I've always thought that quantum zeno effect was overblown

measurement should happen continuously, yes. But that doesn't mean the whole state should be frozen

the fact that it isn't frozen is, from my little understanding, what allows for this whole business of "weak measurements"

> In other words, in an "interaction-free" measurement, there is an interaction, and it triggers the collapse process, which then impertinently deletes it from existence.

In MWI, the deletion part isn't there

cuz the other branch still exists

@Amit I'm not sure, but yes, weak measurements are just usual measurements

I have way too many questions about all this, and no time at the moment to go into this subject in any satisfactory way ;)

@Amit i was thinking : states are global while measurement is local

so the whole state can't be frozen. and i would say it can't be frozen even locally

cuz information will flow from.the outside too

I think the notion is not really defined too well either. For example sometimes the EV bomb tester experiment is considered a type of weak measurement, too. But other people talk of weak measurement only in relation to something you do on an ensemble of states that are identically prepared... so it seems a bit of a loose term

@Amit wiki says it's just a usual measurement

i think wiki differentiates between weak measurement and interaction free measurement

In the Wikipedia they also write "There is no universally accepted definition of a weak measurement"

:P

oh

there is no universally accepted definition of measurement in general too

QM is an incomplete theory :P

lol... runs away

Actually I do need to go ;) good night

good night ;)

@Mr.Feynman quantitative finance