oh

@FenderLesPaul They've been officially banned at my school after a week of someone hoverboarding through the hallways. Admittedly, he was pretty good at it.

::reads chat log:: MAN I make a lot of typos.

@HDE226868 good

they shouldn't be called hover boards

they don't even hover

it's false hope!

sobs uncontrollably

@FenderLesPaul Yeah, it's weird.

Skateboards still haven't been banned, nor have bicycles, so it'll be interesting to see how those go.

One of my buddies at UCSB used to do a lot of X-ray diffraction and AFM measurements.

He'd be in the building late at night.

The machines are on opposite sides of a pretty large building.

He got sick of walking back and forth.

So, he developed a new set of work equipment:

Roller blades

and a bath robe.

'cuz who's gunna care in the middle of the night.

@DanielSank I don't get what the question is about. It states the uncertainty principle and then asks for "some effect" of measurement. What has the "effect" of the measurement to do with the UP?

But then they noticed this on the security footage. Didn't make him stop, just got teased.

Lab chic.

^ Heck yes.

@ACuriousMind Well, for example, if I measure a particle's position, doesn't that mean the position uncertainty is now zero?

Now that I say that, I'm pretty sure someone else asked this more clearly, and I think I wrote an answer...

@DanielSank That's a clear question. I'm not sure how to read that from the question as written, though.

Yeah, it's an inference. I think a little comment in addition to the close votes wouldn't have hurt.

So, first of all, that comes off a little harsh, but whatever. More importantly, to say that the standard deviations are defined without any measurement is puzzling

How can one talk about uncertainties of a thing without considering the measurement of that thing?

This is particularly important in QM where measurement cannot passively glean information from the system without an effect on that system.

Uh...just like you can talk about the expectation value without actually measuring something?

@ACuriousMind You have a notion of an ensemble or something when you talk about probability distributions.

Students tend to get the picture that measurements on the members of their quantum ensemble changes those members, which is correct.

This is a confusing and nontrivial issue.

@DanielSank I have a quantum state $\lvert \psi \rangle$. The expectation value is $\langle A\rangle_\psi := \langle \psi \vert A \vert \psi \rangle$. The standard deviation is $\sigma_\psi(A) = \sqrt{\langle A^2\rangle - \langle A\rangle^2}$. Where's the ensemble?

I agree OP didn't identify it so clearly, and that may not be what they want to know, but I'd bet it is.

@ACuriousMind You're being a theorist :-)

That is entirely possible ;)

All those funny symbols you just wrote down are a way to conveniently represent/communicate a story we tell to explain our data.

From at least one point of view, those funny symbols are nothing more than a really nice way to characterize patterns in a very long list of measurement results, acquired over the decades.

Anyway, the point is that OP knows that measurement changes the state, and wants to understand what, if any, bearing that has on the HUP.

@ACuriousMind (Actually, I think the various ways of thinking about the role of theory are not "that of the theorist" or "that of the experimentalist". They're both important to understand and I use them both.)

(i.e. Theory is both a convenient way to express patterns in data, and a sort of "independent thing" which has meaning of its own)

I would take such discussions to a philosophy chat room, but I find the tone in such places insufferable.

@ACuriousMind shouldn't that be a commutator in the first equation (of the answer you just posted on main)?

@DanielSank No, classically, it's the Poisson bracket

Oh that's classical.

...and I seem to be getting into a fight with Lubos. Great.

^ Heh

@ACuriousMind Though are you rightful?

@0celo7 Ashtekar also seems to use abstract index notation all the time

I should not make answers before going to bed

Pretty sure it's lazy and not very clear

@0537 Eh. I think we're not actually disagreeing about any physics, he doesn't like me saying "velocity doesn't exist in quantum mechanics" and I don't like him saying it does

@ACuriousMind Can't I just define $\hat{v} \equiv \hat{p} / m$?

I realize that's an error prone definition, but it is well defined and sort of behaves how you expect.

@DanielSank Yes, you can, but then velocity is not "distance divided by time", which is what OP wanted to use to contradict the HUP

Hm, reading Lubos' last comment, I think we're answering two completely different questions :D

Which is a bit difficult to sort out in a comment thread

@ACuriousMind you're braver than me. every time he appears in a thread I immediately leave.

just in case I mess up and he posts a 1000 word screed about me on his blog...

:p

@knzhou I think I would find that quite funny

Grahhhh superconducting qubits y u no work!?

@knzhou so true though

I think the most important thing I've learned (after all the technical stuff) is how to ask people for help.

you know I've always loved Kendrick Lamar's mAAd City album but I'd never really paid attention to the lyrics

I randomly decided to and god damn some of the songs have incredibly nice lyrics

I never expected a rap song to be lyrically meaningful; goes to show my prejudice

@FenderLesPaul A lot of people have a weirdly baseless dislike of rap they've never heard.

@DanielSank I think a lot of it is the popularization of "gangster rap" and propagating the false notion that all rap is blanketed under "gangster rap"

@FenderLesPaul Yeh.

Yesterday evening I was in the lab with a theory collaborator.

I asked what music he likes. He said everything except rap.

I was kinda surprised.

That's a response I've heard a lot

and even given myself many times

I used to be way more close-minded in high school with regards to music (and other things but that's besides the point)

I think one of the best things to come out of me going to college is forcing me to become more open-minded in more ways than one, music being one of the important

in high school I basically only listened to blues, jazz, and classic rock

@FenderLesPaul That is without a doubt one of the most important parts of college.

I miss 90's rap.

What's some good 90s rap?

^ lol

YES

@FenderLesPaul One of my personal favorites:

Give it at least to 0:45

lmfao

I lost it at the last one

Nothing funny 'bout fire safety!

@FenderLesPaul

niceee

@BernardMeurer contact me for a contrarian view wrt bohm, bell, nonlocality, realism, measurement "problem" etc

@vzn Hey there! Glad I caught your attention.

@BernardMeurer try the oreilly book on regexps good stuff

@vzn hello man!

hi TM. so B you say you are looking for prjs? comp+physics? are you working on anything so far?

Really? (no puns intended) I'll definitely try it out.

do you know any prog languages? which ones are you learning? see also Computer Science... plz feel free to drop by chat room some/anytime...

@vzn Yeah that's what I think I'm in for, I really love computer science and algorithms and I have a thing for physics so it all blends in nicely

I just got out of highschool and am waiting for my college apps to return. Brazilian applying to the US.

I know Python fairly well, Bash scripting and C

but that's mostly it

how many colleges have you applied to? (good start...) what have you done with coding so far?

9 colleges if you count UCs as one

ok hope the admissions work out for you & you get some choices out of all that. do you have a preference?

Anybody agree with him? ^

I worked for a year and a half on an Open Source company with graphical interfaces and bug fixing. I also worked on a hgh performance factorials algorithm in C3 and C++

*C#

My preference right now is UPenn I believe, because of scholarships, Berkeley is not a possibility currently even if I got in too expensive

@TanMath think you should start working from the simplest possible example that you can get working and then advance from there. also suggest you blog on it somewhere. & then will try to follow your blog.

@TanMath Agree with the second sentence, but questions about fixing specific code are off-topic here, no matter whether we have people who can fix it or not.

Ok...

Thanks...

@BernardMeurer nice what kind of gui? html? what was the purpose of the factorial algorithm? personal prj?

WxPython and some mistery stuff they used to call Kiwi that was a pain to mess with

@vzn can you elaborate on the simplest example thingy?

A little HTML when porting some stuff to phones using Cordova

@BernardMeurer what kind of open source? can you state the company? is it brazilian?

@TanMath suggest you just start with basic qm exercises solved in code. & replicate correct answers. suggest you describe everything in excruciating detail in blog.

Whats a prj? I had no purpose on it really, I just love factorials and it seemed fun. You can read on it [here](www.luschny.de/math/factorial/SwingIntro.pdf) if you're interested.

@vzn ok...

Company was Async Open Source, they do storefront software based on Ubuntu

@BernardMeurer abbrev project

@BernardMeurer close need the http:// in those urls

Ooh, yes it was just a personal project. High school was extremely boring, so I was craving for any projects

Wasn't sure the http was required

@BernardMeurer what major do you want to pursue? fyi here is a near-random list of prjs/ppl from SE chat rooms

@vzn I'm going for Computer Engineering most likely

@BernardMeurer reading the factorial writeup, nice. do you have any interests in number theory?

@vzn I do, but having gone through Brazilian education I don't know much of anything to be honest.

@BernardMeurer hey youre young still time to fix that :)

@vzn That's what I'm currently working on, it's very much like fumbling in the dark

anyway are you interested in bohmian mechanics? CuriousOnes opinions on it expressed earlier reflect the "std establishment" position on it... do encourage you to delve into it as much as possible...

@BernardMeurer ah, "fumbling in the dark". the pastime of the greats. eg Wiles who said so himself once. Newton. etc

so do you want to study physics in college also?

@vzn I am very interested in quantum mechanics in general, the maths is currently a barrier tho

@BernardMeurer ok ... theres a ton to read about QM without necessarily delving into the (admittedly hard) math etc

And yeah I really do want to study physics, it's been my favorite subject alongside maths for a long time now

@BernardMeurer any areas of physics in particular? other than QM?

Interesting, do you have any book recommendations?

Reading about quantum mechanics without doing the math is about the worst path you can take.

@vzn I have a strong curiosity when it comes to fluid mechanics, I'm not sure I like it tho because I haven't studied it much

@BernardMeurer one of my favorites is "meaning of quantum theory" by baggott, a near classic. also "quantum challenge" by greenstein/ zajonc. really liked "infamous boundary" by wick. just a few of many off top of my head. amusingly theres even "qm for dummies" & "qm for idiots" books out. hilarious...

@ACuriousMind I recall you saying that and being met with general agreement

@BernardMeurer ah, fluid mechanics have blogged on that quite a bit. an excellent choice for reasons that are not fully exposed yet.

not everyone is studying to become a physics Phd. there is some strong bias verging on groupthink about that around here.

for nonphysics majors, there are many excellent books to learn the basics of QM... and they should be very much commended/ encouraged for the interest/ effort.

I have seen QM for dummies before hahaha

@vzn You shouldn't do the math to become a physics PhD. You should do the maths to understand what quantum mechanics is. Natural language fails to convey the actual workings - just look at all the questions we get because someone is confused about "things being waves" or the double-slit experiment or any other quantum effect...

@ACuriousMind am not questioning or contradicting your (good! solid!) advice to learn the (hard) math formulas. am only saying, its not the only way, for everyone... learning is not "one size fits all"... think that can be counterproductive at time...

Now the guy says that troubleshooting convergence problems is different and may be allowed here...

@vzn You're making it seem as if "the math" would be the way to learn quantum mechanics. It's not. It's the content, and you cannot learn proper QM without math anymore than you can learn statistical physics without math or Hamiltonian mechanics.

@ACuriousMind I only read about the double-slit experiment and I never truly understood what was going on there

@BernardMeurer join the club

@ACuriousMind Well I guess you can skip a lot of "the" math if you're only interested in aspects of QM Say quantum computing, where I'm not sure if you even need to know the Schrodinger equation to still be able to do interesting stuff. Sure you need to know and do math, but it can be a very different sort of math from the one more obviously inspired by physics.

grr, Duffield...

What's generally considered the hardest math in quantum theory? Say, up to a standard course in QM, QFT up to Standard Model.

@alarge I'm actually puzzled why not more people do quantum computing things in intro QM. The finte-dimensional spaces of qubits are so much nicer to work with than those wavefunction spaces where you always have to evade some technical issues coming from the infinte-dimensional Hilbert space.

@ACuriousMind I got really confused why is it such a big deal while reasing about it. Nowadays I've just accepted it's important and that's it

Quote Feynman: "[the double slit experiment] has in it the heart of quantum mechanics. In reality, it contains the only mystery."

@BernardMeurer It's a big deal because there's no classical explanation, and people would so love to have a classical explanation of it. But, well, you could substitute any other truly quantum phenomenon like discrete spectral lines there, so it's rather a historical accident that it is the double-slit that's so often taken as example, I think

@Bass That is highly dependent on how rigorous you want to be

Standard courses rarely touch upon the functional analytic aspects of operator theory, for instance.

Because only the most pedantic Germans can enjoy that stuff...

@ACuriousMind that is now proven technically incorrect with recent research, there is a classical explanation modelled with oil droplet experiments, not widely known so far

ofc QM computing still has lots of deep math in it, mostly vector oriented etc

@ACuriousMind I see what you mean, I understand it better now.

@vzn I'm well aware of the "droplet" experiments. All they show is that, yes, indeed, a Bohmian-like theory - particle moving along a guiding wave - produces the correct interference patterns. But that's not news. Bohmian mechanics is not classical mechanics.

@BernardMeurer so you think UPenn will give you the best scholarships, or have you been awarded some already?

@ACuriousMind its big, revolutionary news but as gibson (scifi writer/ neuromancer author etc) once said "the future is already here, its just not evenly distributed"... the oil droplet experiments are purely classical...

@vzn I think I have better chances there with them being needblind and so on.

@ACuriousMind I don't know FA well, but I have the impression that the things that would be helpful in a standard physics course are more the definitions (operator convergences) and some examples than the actual theorems and their proofs. Which (standard) physicist needs the proof of Hahn-Banach?

@BernardMeurer "needblind"?

I suppose FA is very important when you do rirogous quantum stuff?

@vzn They show a particle moving along a surface on which a guiding wave can form moves in the ways predicted by Bohmian mechanics. Nobody doubted that - that Bohmian mechanics technically reproduces the results of standard quantum theory hasn't been in question for a long time. So what does the experiment actually tell us that you think is revolutionary?

@vzn They will accept you without taking in consideration your need for a scholarship. Your need for one wont lessen your chances

@ACuriousMind am not actually a huge fan of bohmian mechanics sometimes. see it as contrarian thinking which is in short supply in the field. it is not fully fleshed out. it seems to have a half-baked aspect to it. only think it is "on the right track" etc. and accept all the widespread skepticism of it as inevitable/ unavoidable.

the oil droplet experiments are not strictly bohmian mechanics. bohmian mechanics has other features aka "the pilot wave". there is no direct analog in the oil drop experiments apparently.

bohmian mechanics is incomplete in that it doesnt fully reproduce QM, it does to a large degree but it has edge cases where it fails (afaik).

@Bass Well...you might not need Hahn-Banach itself, but you surely need the infinte-dimensional version of the spectral theorem, for instance

@ACuriousMind my opinions about the revolutionary nature of the experiments are written up at length over several blogs now, its too much to summarize here...

Sigh...my parents bought me a coffee machine and it's too big to fit anywhere

also, rome wasnt built in a day, and revolutions can take a long time. the QM revolution took place easily over at least 2 decades or so... starting in 1905 and possibly ending with nobel prizes awarded in the 1920s etc...

Does anyone have a bright idea for this coffee machine

Maybe I could put it below my bed...

@BernardMeurer other colleges dont work that way? thought the scholarships vs admissions were somewhat independent at times...

@BernardMeurer I use the double-slit experiment very often as a model to "test" some quantum thing I'm thinking about or which I have just learned. I specially like the aspect that you can do the same experiment with macroscopic particles like bullets and with waves like light or waves on a water surface. The quantum version has aspects of both, but it shows that a quantum particle is neither.

@vzn At least one major group doing those experiments explicitly calls it pilot-wave theory, and the original work by Couder and Fort also relies on the particle coupling to the surface wave. It's nice to actually have a lab system that behaves pilot-wavy, but, again, no one ever doubted such systems would behave like that.

@ACuriousMind the behavior was utterly unknown to the founders of QM at the time...

So? It wasn't unknown to us, at the very least since Bohm

@ACuriousMind it is pilot wave theory roughly, in spirit, but not exactly.

@vzn not all of them, and UPenn has a lot of scholarships. @Bass That's cool! I think all of this bus be much easier to understand when you're able to get some sort of visualization.

oh, it fits

turns out it was not upright in the box

@ACuriousMind there is a constant "moving the goalposts" by mainstream physicists vs bohm. its tiring & not strictly intellectually honest.

@vzn That's an interesting assertion which I won't believe without specification of those "mainstream physicists" and proof ;)

the statement "no one ever doubted such systems would behave like that" is not accurate/ misleading. no one was aware such systems existed

obviously you are just playing devils advocate with all this anyway...

these instructions should be GTM books...wtf

or should we say, me as devils advocate and you as devils adversary? :P

I think this is the same coffee machine as in the Senate office!

@vzn The counterpart to the devil's advocate (advocatus diaboli) is god's advocate (advocatus dei)

(Both are actually names for certain jobs in the Catholic church)

get out of here with your Latin

@ACuriousMind lol whatever stand corrected :P

and the monks argued how many angels dance on pins too, right? my college philosophy teacher insisted all that was just an honest misunderstanding lol

How do poor people filter tap water?

I need a solution

@0celo7 Depends what you're trying to filter out.

All too often the answer is "they don't" or "ineffectively".

@dmckee whatever makes my coffee machine last less longer

@0celo7 here in Brazil we filter it by drinking it and hoping for the best

@vzn Yeah, they did. It's intrinsically linked to the old scholastic worldview, and doesn't make any sense whatsoever outside of it, which is why it's used as an example of "theology gone wrong".

@0celo7 Use bottled water or just clear it with vinegar every month of so.

I don't have money/room for a whole filter apparatus

@dmckee >vinegar in a dorm room

You wanna make the trip to TN and do that for me?

No, I only clear ones I have to drink from. That's your coffee machine, not mine.

@ACuriousMind how about another ref to the middle ages?

well you can drink from it when you're here

You can actually use any food-safe weak acid, so ask the chemists...

like vomit HCl?

I recommend sulfuric

@Secret I need your help

HCl is a strong acid. Bad for the metal bits.

Oh yeah

@Secret I need a homemade weak acid

At least nitric doesn't etch most stainless steels.

Can't you just buy citrus acid used for cleaning?

I wonder how much the standard descaling stuff is.

@ACuriousMind I'm sure I could buy the proper cleaning stuff...

@vzn Necessarily true of all of science

Come to think of it, you can sometimes find powdered citric acid on the spice aisle. Might be more convenient to store.

Was thinking of that^

The only convenient store nearby is a Mega-Walmart.

Because it's cheap, and you don't have the danger of spilling a bottle

If I had wheels I could go to Costco.

But alas, not this semester.

@ACuriousMind thx for keeping me on my toes. fully admit, bohmian mechanics is half baked. oil droplet experiments are half baked. conclusion is: it all requires more baking!

@vzn Now that I can agree with :D

frustrating: this paper definitely exists, but was only published in an obscure volume of an obscure periodical, that appears to not even be in the UC library

oh my GOD my phone turned off push email

@ACuriousMind lets turn the tables on this one. arent there areas of physics research youre interested in? terra incognita? you have to start a masters thesis soon right? or was it Phd?

wonder how many I missed...

@MikeMiller Request it from the Library of Congress.

@vzn Master's thesis, yes. Looks like I might be doing either stuff on moduli space or stuff on 3D Chern-Simons, nothing concrete yet, though

@0celo7 good point actually

@ACuriousMind ok. is that string theory?

@MikeMiller I worked as an intern on Capitol Hill, I have an LoC card. They tell you any U.S. library can request a volume from them.

@0celo7: Pretty cool, thanks. I'll bug my librarian about it on Monday.

It might take a while, of course...but if you really need it...

i am patient.

@vzn It's not explicitly stringy, although the boundary between this part of quantum field theory and string theory is not very clear

@ACuriousMind have I been doing string theory this whole time??

@MikeMiller Perhaps. No doubt some string theorist is interested in the moduli space of some gauge fields, too

a terrifying prospect.

String theory as such is actually not that different from quantum field theory

@ACuriousMind seems much tied up with witten, who is much tied up with strings.

@vzn Half of theoretical physics is tied up with Witten ;)

string theory, a theory in search of an experiment... for decades...

And I'm not sure that's a hyperbole

certainly half of mathematics is

maaaaybe only a fifth

this mug has not been washed in months

↑ you call yourself a physicist? :P

Combinatorics?

Theoretical physicist. Maybe even mathematical.

Is there anything useful from that field besides the binom. theorem?

@0celo7 Graph theory.

what's that

The theory of graphs.

wow

what does it do

Talk about graphs.

@ACuriousMind The QED Lagrangian's interaction term is $e\bar\psi\gamma^\mu A_\mu\psi$ right? Now, I have read that there are photon-photon interactions (although with very small amplitudes). Does such an interaction term allow for a direct photon-photon interaction? Or does one need another theory to describe it?

@ACuriousMind any interest in anything applied? or did you skip all those classes? (maybe optional in your case?) :|

graphs

With just one photon field operator, I cannot see how two photons could interact.

@Bass at 2-loop level. Look up "box diagram"

@vzn To finish off, if you're looking for someone to give you a hand with any projects I'm more than up to it.

@BernardMeurer wow thx! have been banging on a number theory exploration for years now. its quite hairy. more details in blog. lets keep in touch. am sure you will find something worthy/ worthwhile sooner or later to occupy you.

@vzn Did my share of labs, heard my share of experimental lectures, but no, I'm not interested in applied things. I'm also not actively disinterested, it just doesn't excite me, while theory...does, for some reason.

@ACuriousMind no, the photon is really just an electron going round and round

@0celo7 I shouldn't have unblocked you.

@ACuriousMind fair enough.

@vzn Could you send me a link to your blog once again?

@ACuriousMind :(

@BernardMeurer (click on my blue hyperlinks earlier in transcript, in my profile etc)

my new coffee maker's coffee tastes very different than the old one's

@Bass: After looking up "box diagram", look up "penguin diagram" and read the origin story ;)

@ACuriousMind Oh I see. I expected a Feynman diagram where the edges of two photons share the same vertex, but okay, makes sense.

@vzn, got it!

@BernardMeurer hang out in this chat room, n00bs always welcome, see/ search long history/ transcript :P

bye nice chatting

cya

@0celo7 Do they differ in some way other than age? (method, cone shape, etc?) Sometimes you need to change the grind when you switch machines.

@dmckee it's a Keurig

too poor for that grinding stuff

this coffee tastes less burnt

@0celo7 Er ... K-cups are about the most expensive way to buy coffee short of actually going to 4bucks.

that taste is why I got rid of the old one

but this French Vanilla does not taste like vanilla...

But I have no idea when or how to clean a k-cup machine.

@0celo7 Oh .... I see. You're one of ... them. Where is that blocking function, anyway.

@ACuriousMind :D Beheaded penguin diagrams would have been more accurate, but apparently he was on a good trip.

@dmckee One of what?

I also drink dark roast. It depends what mood I'm in.

I have 4 different flavors. And for God's sake please don't think I use sugar and milk/creme.

Coffee antichrists. They're everywhere.

@Bass An informal survey shows that a majority of physics students agree it "kinda looks like a penguin, now pass the joint"

I like $buck's and Panera's hazelnut blends.

@dmckee Who is coffee christ, then?

And was he roasted instead of crucified?

That's Phil.

@ACuriousMind Not a clue, but come the millennium there will be Blue Mountain and Kona for everyone.

@dmckee After blowing my nose and aromatically tasting the coffee like a fine scotch I can discern faint hints of vanilla.

It's not as powerful as the taste my old machine put out.

@dmckee Am I an Antichrist for liking other things in addition to dark roast?

I don't care how you roast it. And I certainly don't care if you have some milk (or better some foam) with it. But covering the flavor is a sin.

Covering?

Nae, augmenting.

@ACuriousMind Is the Well Ordering Principle for $\mathbb{N}$ an axiom of $\mathbb{N}$?

I know it can be proven if ZFC is true.

@dmckee Does "Pacific Bold" meet your non-Antichrist criteria?

@0celo7 Ill-defined question, since there are different axiomatizations of $\mathbb{N}$.

@ACuriousMind So there are models where it must be proved?

My algebra book calls it an axiom, the prof stated it and then mumbled something about set theory definition of natural numbers.

@0celo7 The Peano axioms, for one, don't have well-ordering in them. You have to show it from the statements about successors.

@ACuriousMind Ah, that might be what he was talking about. Thanks.

And I'm sure @yuggib would also have you prove it from his favourite definition of the natural numbers ;P

@ACuriousMind The prof does arithmetic geometry so he might like that definition too...

@ACuriousMind Is it reasonable to say that one of the reasons we math people like traditional tensor notation is because of all of the pushforwards and pullbacks we use?

If $\omega$ is a $p$-form it's not fun at all to write $\phi^*\omega$ in indices.

@ACuriousMind How is addition defined in the set theory model of the natural numbers?

@FenderLesPaul Exactly. Cf. e.g. Move Bitch for some lyrics that make you think