The h Bar

8:00 PM

And also I was quoting myself (in real time)

So I could just copy paste:

"In physicsstackexchange were okay with the above quote ... And even if brought to our attention ... It okay!"

Is the essence of what ur saying?

Also QM was taught in year 2 in my unversity and Im sure there are those with year 1

bolbteppa

@MoreAnonymous you still haven't pointed out how 'discontinuity and non-unitarity of measurement' even apply to this derivation

More Anonymous

I feel I have done so many times (in fact Im not sure why you feel otherwise) ... I feel Acuriousmind can represent my position better than I have ...

Maybe he is more suitable

And you should ask him the very same question

ACuriousMind

@MoreAnonymous A counter-anecdote: I learnt QM in my 4th semester (so 2nd year) where this exact derivation of M-T time-energy uncertainty was presented. I didn't see anything wrong with it then, and it did not lead me or my peers (that I know of) to unfounded conclusions.

Semiclassical

@bolbteppa I’d actually agree on this: the derivation is very much predicated on unitary time evolution. But that’s exactly the context in which it is relevant

ACuriousMind

Whatever is causing confusion, I feel strongly it is not, or at least not mostly, this particular derivation or the lack of giant CAUTION signs around it

More Anonymous

8:06 PM

@ACuriousMind I feel you and your peers were more than us mere mortals plus ... I feel your saying the average opinion I have encountered is a statistical fluke ... which is a posssiblility but still an improbability

Semiclassical

So to complain about it not addressing the case of non-unitary evolution is to complain that it’s answering a different question than the one you want

ACuriousMind

@MoreAnonymous We were of flesh and blood and caffeine as you are.

More Anonymous

@ACuriousMind I used to think the same of Einstein :P ...

Also are u of the opinion what Ive encountered is a statisical fluke or not?

ACuriousMind

@MoreAnonymous No, I'm well aware there's a lot of confusion around this. We just disagree as to what's causing it.

bolbteppa

@Semiclassical if I understand you right I agree, I have no problem with that, my question is really though - how does non-unitary time evolution even relate to this discussion

I think we talked about non-unitary Hamiltonians or Non-Hermitian QM on here before done by respectable people

JBis

8:09 PM

Hi o/

I'm a student and am a bit confused on the conservation of energy.

ACuriousMind

hey there

More Anonymous

@ACuriousMind Can we agree we can minimise the damage by adding a few lines (maybe putting an edit in bold so those who want to read that section can?)

???

Even if not minimise we can lessen/

?

ACuriousMind

@MoreAnonymous You're free to suggest an edit, but as I said I do not think that what you want that answer to say is at all relevant to the specific question it is answering.

JMac

@MoreAnonymous If you think something is wrong/misleading, downvote and leave a comment. Or just leave a comment if it's a small error

More Anonymous

@JMac I left a comment ages ago ... But it didnt get answered let alone upvoted

And I lost patience and asked a question

JMac

8:11 PM

@MoreAnonymous Well then clearly your concern doesn't seem to reflect the rest of the community. Not much else you can do there.

JBis

So take a runner for example. We can see energy transfer from place to place. Sun → Grass → Cow → Runner. But once the runner starts running, where does the energy go? Obviously the runner is using energy to run (this is known because they cant run forever), but the energy doesn't seem to transfer anywhere.

ACuriousMind

@JBis friction with the ground + movement of the earth (imperceptible since its mass is so large compared to the runner)

JMac

@JBis The air, the ground, body heat, sounds. It basically "dissipates".

More Anonymous

@JMac nope Acuriousmind is under the opinion that people of the community are unaware (if not misuing) this derivcatoin and hence it involves the whole community

JBis

@ACuriousMind so you are negligibly slowing or speeding the earths spin?

ACuriousMind

8:13 PM

@JBis Among other things (heating the ground and air through friction, etc.), yes

obligatory xkcd

JBis

Hmmm.

Ok so what about mass → energy and energy → mass. Isn't energy lossed/gained there as well as matter, breaking both the conservation of energy and conservation of mass laws?

More Anonymous

@JMac Also it is highly intimidating to think you are right when your against a 90 upvoted question (I mean if u do then ur on crackpot level) ... And a user like me shouldnt have to pay the price of downvotes on a seperate question regarding some legtimate (doubts) ...

I feel physics stackexchange has let me down ...

:(((

ACuriousMind

@JBis 1. There is no "conservation of mass". 2. $E=mc^2$.

bolbteppa

In special relativity, energy and momentum are constrained by $E^2 - \mathbf{p}^2 = m^2$

JBis

Oh

More Anonymous

8:18 PM

Also @ACuriousMind will you be willing to continue our discussion where I make the case a few more lines can really minimize the damage?? (I can wait if ur teaching) ... Or ...

JBis

> The law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy,

JMac

@MoreAnonymous Welcome to the internet, things are going to let you down. Doesn't mean that you just to change things to fit the way you want to see them, when others in the community don't seem to agree. I'm not saying you're necessarily wrong or anything, but adding disclaimers to answers because you find something misleading isn't the correct approach on SE.

JBis

What about conservation of energy?

bolbteppa

@MoreAnonymous he's basically just quoting a section from Griffiths QM book, I really don't understand what the problem is with the derivation apart from hand-waving worries that 'continuity' and 'unitarity' somehow don't apply because ... (coupled with hand-waving worries about unnamed alternative interpretations maybe disagreeing)

JMac

@JBis What about it? For most classical systems, assuming that all mass remains as mass and all energy remains as energy is fine, and in that case both are independently conserved in a closed system.

More Anonymous

8:21 PM

@JMac I suspect if an answer doesnt enlighten the user to what physical case it is relevant in then its not really a great answer ... I mean if you scroll up you can see other chat users making the case for this derivation in cases it clearly doesnt apply to ... In which case "you" is the wrong word ....

ACuriousMind

@MoreAnonymous I'm sorry. But I feel I have said all that I can say (multiple times, in fact). I have explained why I think your question is problematic even if your underlying confusion is earnest and legitimate, and I have explained why I think josh's answer is a good answer to the question it is written as an answer to. You seem to have different expectations of what an answer here is supposed to do, and that is fine, but I simply do not agree.

More Anonymous

Hmmm ... Oh well ... thank you for being clear on this and atleast letting me making a case for otherwise ...

JBis

@JMac So are there exceptions?

More Anonymous

I appreciate your franknes

JMac

@MoreAnonymous Well, your suspicions don't really align with how this site works... The answer clearly provided some information that others found useful, hence it was well received. You don't get to add things to it just because you didn't personally receive it as well. This site would turn into a mess that way, and that's basically my only point.

More Anonymous

8:24 PM

@bolbteppa ... maybe if acuriousmind if up for it he can convince you why "(my) underlying confusion is earnest and legitimate"

bolbteppa

There's about six other answers on there as well lol

ACuriousMind

I fear if I say "measurement is a black box" one more time the ghost of von Neumann will appear and bludgeon me to death with a giant ket.

bolbteppa

@MoreAnonymous it's fine to be confused about the derivation and to have concerns things don't apply, that's basically the whole point of studying physics is to question things until you're convinced, but honestly you have ignored multiple direct questions from me written in multiple ways asking you to directly point out why your concerns are even relevant and you haven't done that yet

ACuriousMind

(More seriously, I'm just tired)

More Anonymous

@JMac You keep saying "you" and I would agree with you if it were just me (I feel above 50% of the users have my misgivings) .... Acuriousmind seems to agree my experience is not a statistical fluke ...

@bolbteppa I feel like youve ignored my direct answers (I notice I use the wording feel)

JMac

8:26 PM

@JBis To just the conservation of energy, there are kind of exceptions; but not really. Mass and energy are treated as equivalent. As far as energy conservation in introductory physics classes are concerned though, you typically assume mass and energy are separate and don't convert between each other

bolbteppa

@MoreAnonymous Can you send a link to even one of your direct answers

More Anonymous

I mean you link some of them to acuriousmind ....

JBis

Ok thanks for the help, I'm sure I'll need more soon

:)

bolbteppa

There is an arrow on the left of each post, click and then see the "permalink" thing, send me that link to even one direct answer

More Anonymous

@ACuriousMind if your tired Im braindead by this point

bolbteppa

8:28 PM

@MoreAnonymous I would call that a dodge haha

I'm going to make a bold claim that I can also permalink my response to that post :p

JMac

@MoreAnonymous Still not really my point. My point is that just because you and possibly some others find some issues with the answer, doesn't mean that you should substantially change what someone else's answer is saying. It's just not how this site is supposed to work. The community works together, but it's not like we're a wiki. People have their usernames attached to the posts, so changing content of others is best left alone.

More Anonymous

@JMac So your okay with above 50% of users misinterpreting and then misusing the answer ???

If you say yes ... we will reach an agreement instanansously

ACuriousMind

I'll let you in on something: There are upvoted answers on this site that are flat-out wrong! Yet we do not delete them because that is not how we do things here: If it is an attempt to answer the question, it will be judged by votes. If the wrong stuff gets upvoted, that is a failure of the community, but not a failure we would remedy through edits or deletion.

JMac

@MoreAnonymous I have no control how others chose to use information they get online, so yes, I'm fine with it. People can misinterpret any answer on this site if they want to.

More Anonymous

@JMac And your okay with it being above 50% as well?? Im quite saddened to hear that ...

bolbteppa

8:34 PM

@MoreAnonymous I linked about 7 posts of yours above where you asked questions, not one of those things I linked is an answer to even one of my direct questions about why non-unitarity of measurements even matters to the unitary evolution described by Heisenberg's equations used in the time-energy derivation, it's comparing apples and oranges and you still haven't explained why it's an apples to apples comparison

More Anonymous

I only use question marks due to sheer disbelif

@bolbteppa honestly my argument seemed to make sense to Semiclassical and Acuriousmind who (I feel) engaged with me ... And they all had access to typing (as do you) ...

I suspectr it would take alot of effort for you to even see why I said what I said ... let alone ever sympathise with it ... And hence I advise you should ask those who understood me ... I am far too exhausted right now and mentally fatigued ... and Now after witnessing the brazen "its okay" policy Im questioning the frequency I'll visit the site (let alone the chatroom)

@JMac @ACuriousMind ... I suspect the real reason stackexchange has the elitist sterotype is becasue perhaps the intellectually elite have given up on this system ...

bolbteppa

@MoreAnonymous I'm so aware of the fact that you're hinging on the hope you at least convinced someone of your concerns that earlier I already pointed out you used an apparent understanding on other users part to claim that "the measurement problem implied that the Heisenberg equations sometimes did not apply" chat.stackexchange.com/transcript/message/51657961#51657961 which is absurd, this is not a good way to gain an understanding of the topic you asked for help with tbh

You're actually disagreeing with a section from a Griffith's book and trying to blame the site for Griffith's explanation of time-energy at this stage

More Anonymous

Yes ... Maybe at this point I am too mentally fatigued to understand why you disagree (without the use of non sequitors) ... And hence I 'll be leaving the chat soon ... I apologise for not being able to have the intellect or the perseverance to convince you ... But others might ...

bolbteppa

No worries, you don't even have to convince me of anything, just asking you to explain your how concerns are even relevant to the derivation

JMac

@MoreAnonymous What? What does the elite giving up on the site have to do with "elitist stereotypes"? Wouldn't you expect the opposite correlation if anything? Also, I don't go around looking up other opinions of Physics SE, so I can't even speak of this elitist stereotype you speak of.

More Anonymous

8:48 PM

Anyway I'll be dropping of for the chat .. Let me just add this is the first time I feel let down by physicsstackexchange .... I feel upto this point it has been a gr8 experience (in fact I feel emotioinally run down becasue it has been so gr8) ... Atleast my doubts were clarified in the end albeit in an unusual way

bolbteppa

I'm sorry a virtual quote from a section of a Griffith's QM book being the top up-voted answer has upset you so much, take heart that people tend not to like Griffiths' books :p

Slereah

Man trying to think of schemes for measuring distances properly in GR is hard

I can't even assume that the distance won't increase by more than $ct$ with time because space expansion can 100% do that

bolbteppa

@Slereah curveball - the measuring device isn't even a rigid body and so can't even be trusted beyond a certain accuracy

Slereah

@bolbteppa Well i'm using light signals here

ACuriousMind

@Slereah Wait until you get to measurement stacks!

Slereah

8:52 PM

but of course, also consider this : the gravitational field will change the frequency of the atomic transition

Since that adds another potential to the Dirac equation

I mean that one I choose to ignore because come on

I just assume that my measuring device is some perfect device full of lasers, light detectors, clocks, memory and computing units that is exactly a point

bolbteppa

I'm always just assuming you do measurements in a locally inertial frame where everything's fine

Slereah

The current problem is the ideal case : consider some 2D spacetime $(\mathbb{R}^2, g)$, with $g = \Omega^2(x,t) (-dt^2 + dx^2)$

It is foliated by timelike curves, which are observers

At every point in time, each observers emits two light signals (one forward, one backward)

More Anonymous

@JMac (only since you guys pinged) ... Nope I use the word intellectually elite ... And I feel your doing what the user below was doing
@bolbteppa it wasnt the quote ... it was the price I had to pay to learn if anything ... Esp for a site which is supposed to enable "learning" ... I suspect you do not take my advise of asking semiclascial or acuriousone seriously ... Because of this "price"

Slereah

each light signal encodes informations about its observer of origin, what proper time it was emitted at, etc

Given all this, can one observer reconstruct the entire metric?

@bolbteppa That's the easy way, of course

But that's making pretty large assumptions

Even worse, unstated assumptions!

It's pretty hard to do because even just making sure that all observers are synchronized isn't trivial

JMac

@MoreAnonymous I literally don't understand how your response relates to our conversation. I when I said "elite" I also meant "intellectually elite" just like you had said.

Slereah

8:58 PM

If I assume everyone synchronized at some Cauchy surface $t = 0$ I think it should be easier

bolbteppa

@MoreAnonymous come on haha this is getting hilarious, asking me to ask other people whether they understood you and asking them to reiterate back to me their understanding of your point, even though I have already literally given an example where you got people to say things that you interpreted as validating a beyond absurd claim? Is this for real?

Slereah

Although of course

Here's another problem

HORIZONS!

What if some light signals never arrive to you???

Hopefully I can at least reconstruct the metric in some neighbourhood

ACuriousMind

@Slereah You could say you'd stay in the dark about them.

Slereah

Indeed I can

More Anonymous

@JMac Are you saying the IQ points of this "intellectual elite" is so much that they wont make sense to the people wo misunderstand (in this case more than 50%) ... atleast I for one am an outlier on that one

Slereah

9:00 PM

why can't we just live in Minkowski space, really

bolbteppa

@MoreAnonymous 'the intellectually elite have given up on this site'... 'alternative interpretations'... 'quantum equations of motion can fail sometimes'... I mean, there is a way to describe statements like these...

ACuriousMind

@MoreAnonymous I have to say that nothing you've said pertaining to "elites" made any sense to me either.

JMac

@MoreAnonymous Not even slightly... wtf? You said that stackexchange has an "elitist stereotype" because "intellectually elite have given up on this system", and it's very unclear to me how that follows.

bolbteppa

(I thought I was in the elite, until today...)

Slereah

I mean

Things are hard enough in Minkowski space

More Anonymous

9:03 PM

@bolbteppa it must be pretty easy to convince yourself that the others are "validating a beyond absurd claim" ... Rather than think ur being absurd ... I feel they arent taking a side because they dont wanna ... Maybe someother price

bolbteppa

The elite live in Minkowski space

More Anonymous

@ACuriousMind yes and i never said you did

Slereah

I'm not even sure how easy it is to reconstruct synchronization for accelerated objects

Because the usual synchronization is basically just a Lorentz transform of the foliation

But once it's non-linear

Anything goes

ACuriousMind

@Slereah can we not just pretend we do? :P

I mean, sure precession of mercury is gonna be off a bit, but otherwise, what'd be the difference? :P

Slereah

@ACuriousMind Can't go back to the garden of eden, I'm afraid

More Anonymous

9:05 PM

@JMac to me its pretty clear in this case Im refering to those who get that context of that derivation as intellectually elite ... I feel they enough points to make a difference .. But maybe thats where Im wrong ... And the "elitist sterotype" prevails in this case because the elites do not wanna make the effort?

To correct the idiotsw (like me) ... From idiocy

Slereah

Why wouldn't you listen to the intellectual elite, really

Sounds like they know what they're talking about

bolbteppa

@MoreAnonymous are you saying I am being absurd in asking you to simply state (or even re-state) your concerns about a topic, rather than taking the easy way out and asking other people to state your opinion for you

JMac

@MoreAnonymous I'm having increasing difficulty following you... so I'm gonna head out and get a coffee because this doesn't seem to be going anywhere

More Anonymous

@Slereah I did listen to them and hence gotan answer finally ... But Im not sure everyone else with this problem (more than 50%) would be willing to pay this "price"

Slereah

@ACuriousMind The thing is that the parameter of the Reichenbach synchronization, $t = t_1 + \varepsilon (t_2 - t_1)$, is basically the "tilt" of the Cauchy surface

More Anonymous

9:08 PM

@bolbteppa I dont care about the opinions of Lee Smolin or Lubos Molts I care about the arguments they make

Slereah

So I'm pretty scared that for a generic Cauchy surface it's gonna be some awful function

More Anonymous

@JMac Agreed Im gonna go for sleep though

Slereah

But the hard part is making sure that the synchronized points are spacelike separated, at least

bolbteppa

@Slereah but why can't you take the easy way out since GR reduces to SR locally

Slereah

@bolbteppa Well that's the thing

how locally?

(I mean I know that in real life that's obviously true at human scale)

But it's one of those things where like...

More Anonymous

9:10 PM

@bolbteppa also in this case I feel they understood my arguement and will not misrepresent it ... In fact they will do my concerns better justice ...

Slereah

I like to show the general case to show that the approximation is valid

bolbteppa

@MoreAnonymous are you sure they weren't just saying it's understandable for someone to have legitimate questions about a derivation and nothing more beyond that, seems like a big stretch to assume other people got your point when you can't even quote a single passage where you made this point after directly being asked to do so

Rather than making a gigantic presumptuous assumption about other people, it's probably safer to just re-state your point or even just post a link to where you made this point

At this stage, I'm going to say you can't

ACuriousMind

I agree with JMac that this doesn't seem to be going anywhere useful and would ask everyone to drop the topic for now.

bolbteppa

Okay, last thing: lol

Slereah

And of course

If we're just assuming physics as is

No point in doing any research

More Anonymous

9:16 PM

@bolbteppa No I precisely feel even though you hear people say "on this point I agree with him on this point"... "I'm disappointed that the answer doesn't address the question I wish the OP had asked." ... Also acuriousone personally pinging you and telling you that this derivation does not have imply the physical situaiton you think it does ... You have convinced me (and perhaps not only me) it is not worth the trouble

Sorry I just read your comment acuriousmind ... I was amidst typing the above comment

bolbteppa

@MoreAnonymous super last thing, really quick, I think you read the "I'm disappointed that the answer doesn't address the question I wish the OP had asked." sentence unironically, I think you need to re-read that one

@Slereah have you got any links to these issues with GR measurements (that don't involve crazy global GR)?

Slereah

@bolbteppa As mentionned, the only extensive treatment I know on the topic is Reichenbach

bolbteppa

But like, even a popular article on the issues with GR measurements related to these topics

Slereah

There might be others in the more philosophical-oriented GR books like maybe some of Malament or Earman's stuff, but I can't think of any rn

Well today i found this, for instance :

adsabs.harvard.edu/full/1992CeMDA..53...81K

More Anonymous

I have no idea how high the sarcasm level you think in this chat is ... But I disagree because u have also "I'm allowed to be wrong :)" ... Where he admits the position he took was wrong and only got to know the answer because of a user like me ...

Slereah

9:24 PM

It's pretty hard to work out in GR because there are so many things that can go wrong

bolbteppa

This is all probably part of the GPS relativity (engineering :p) literature

Slereah

Well I think in the actual literature they just assume that earth is ~ a kerr metric

They don't go building an interferometer every meter of space

Slereah

9:48 PM

They see that the earth looks about round and don't go start thinking "Maybe it only looks round because of the geometry of space!!!"

that way madness lies

(it's by the way kind of what Reichenbach discusses)

the how can you know what the geometry of space is without too many assumptions

More Anonymous

@bolbteppa ... I feel I should try to clarify my stance with you .However, I am already of the impression that it will take more than this one chat session ... Are you up for it?

ACuriousMind

@Slereah ...have you become some kind of GR flat earther?

Slereah

@ACuriousMind Not so far!

bolbteppa

@MoreAnonymous sure

More Anonymous

@Slereah if I'm sure r/earthisflat would love whatever u've done :P

Slereah

9:52 PM

I mean even assuming weird geometry it still has to be diffeomorphic to a sphere :p

Although it could be a cube I suppose

More Anonymous

Alright Lemme see where the disagreement comes from?

bolbteppa

Synchronized atomic clocks ftw

More Anonymous

Do u disagree that the measurement (naively) cannot be represented by a unitary transformation?

@bolbteppa

bolbteppa

I don't know what it means to represent measurement as a transformation tbh

Slereah

Part of the issue is assuming that measurements are a transformation on the wavefunction

I'm not sure that's a good argument to make

although of course it's a bit weird because quantum probabilities aren't Kolmogorov probabilities

More Anonymous

9:58 PM

You should find this post enlightening on why whatever the measurement is why people are not comfortable saying that the measurement is a unitary operation

3

Q: Why isn't transformation, caused by measurement, unitary?

It is said, that when measured, a quantum system undergoes "wave function collapse", which is a non-unitary transformation. Why? The wave function is $\Psi = \alpha \left|0\right\rangle + \beta \left|1\right\rangle$ where $\left|\alpha\right|^2 + \left|\beta\right|^2 = 1$ The probabilities...

bolbteppa

A measurement is an interaction between a measuring apparatus which is (quasi-)classical and a quantum system

You can model this, it's in Landau's QM section 7, I don't want to quote the whole thing, but this wave function collapsing business is pretty straightforward there without all the woo

More Anonymous

Maybe you should answerr this question ... I would find your answer quite enligthening

(the physic stackexchange post mentioned above)

Slereah

A measurement of a state from the subspace of the Hilbert space $H_1$ by an observer of the Hilbert space $H_2$ is an evolution of the form $$|\psi_1 \rangle \otimes |\psi_2 \rangle \to \sum_{\alpha} c_\alpha |\psi_{1,\alpha} \rangle \otimes |\psi_{2,\alpha} \rangle$$

bolbteppa

That question is basically modelling measurement as a projection without even considering the measuring apparatus etc

Slereah

This is all extremely unitary

Of course the observer doesn't see it this way because he too is part of the system

More Anonymous

10:01 PM

Okay if thats your interpretation of quantum mechanics you have to answer why is the apparatus (quasi-)classical sytem and another quantum system ... Why does it fail to make model it as 2 quantum system ... you have to answer why the experimental apparatus is special?

Slereah

The experimental apparatus isn't special at all

cf above

It's just another ray in a subspace of the Hilbert space

bolbteppa

@MoreAnonymous check out section 7 of the book I just referenced, it goes into this, but basically the theory as it stands was constructed for this to be this way, to end up with eigenvalues as the measurements, the wave function collapse is just a consequence of linearity

More Anonymous

yes .. but bolbteppa is of the opinion its k to say the appartus is (quasi-)classical

ACuriousMind

@Slereah That aside is crucial. You've described measurement as seen "from the outside" by some observer who hasn't interacted yet with either the system or the measurement apparatus.

More Anonymous

@Slereah ^

Slereah

10:03 PM

I mean it's like saying if you turn a pen on its side it shrinks because you see it become smaller :V

More Anonymous

@bolbteppa I do not doubt the result of this modelling ... I'm asking why you are allowed to do it in the first place

?

bolbteppa

Measurements are actually readings of the apparatus

More Anonymous

Why not just use one quantum sytem to "measure" another?

ACuriousMind

@MoreAnonymous Quasiclassical just means that the apparatus has macroscopic "pointer states" that the experimenter can in turn "measure" by just looking at it.

Slereah

You can describe apparatus as quantum systems

It's less pleasant but it has been done

ACuriousMind

10:05 PM

We're going in circles, again, because this is just decoherence/von Neumann measurement scheme mentioned waaaay earlier.

Slereah

But then you have to make sure you're comfortable of yourself being in a superposition of reading one number and reading another

@ACuriousMind Well as I said

We already talked about this in 1927

I wanted to talk Navier-Stokes but no

Everyone wants the quantum

ACuriousMind

@Slereah Unfortunately, I'm not fluent in fluid dynamics :P

Slereah

Oh neither am I

But it seemed more pleasant than another rehash of the usual quantum conversation

More Anonymous

@bolbteppa Im guessing u believe that decoherence solves the measurement problem entirely but not even Wojciech H. Zurek takes this extreme position

ACuriousMind

@Slereah I am increasingly inclined to agree

JMac

10:07 PM

I've taken 3 or 4 courses specifically about fluids, and my understanding of the N-S equations is very limited. That stuff is pretty wild when you dig into it.

ACuriousMind

So you'd say it's turbulent? ;)

More Anonymous

@ACuriousMind @Slereah Its either this or reform the answer!! :P .... So I dont have make the world a better place :P

Slereah

There are plenty of books you can read on the topic of quantum shenanigans

Streater and Jammer are two good ones

Jammer is actually pretty good because it opens with an actual definition of what a physical theory is

More Anonymous

@bolbteppa I'm also curious of your solution to Wigner's friend (thought experiment)

ACuriousMind

@MoreAnonymous No, it's me asking you and @bolbteppa to take this to another room if you really want to continue this discussion. We've been talking about this for hours now and there has been little evidence of progress, and other people seem to tire of it, too.

More Anonymous

10:10 PM

I dont think I have enough points to even open a chatroom and I know if that relevant since I havent done so in the past ....

:P

bolbteppa

Just read section 7 of that book basically, I don't have any extra insight

More Anonymous

hmmm ... k ... I'll have to take time and get back to you ... It will take some time esp since I am messed up for office tomorrow

Must sleeeep

Feel free to ask the question "does de-coherence alone solve the measurment problem?" till then

bolbteppa

@Slereah What is a fluid but a special case of quantum stat mech :p

Slereah

@bolbteppa Well that's the thing!

From what I hear, there is currently no derivation of Navier Stokes from a stat mech system

that's pretty strange

bolbteppa

Right, there's no full quantum non-equilibrium stat mech yet

It's just incredible how hard CM, EM, GR, QM,QFT, SUSY, SUGRA and strings are that there's no time to do stat mech and fluids etc properly

ACuriousMind

10:24 PM

I think you vastly underestimate how many people are working on things like fluid dynamics vs. strings/SUGRA there

Slereah

Well fluid mechanics is certainly more lucrative

The oil companies don't extract so many superstrings

bolbteppa

haha

Slereah

Just doing CM is already hard enough if you do it weirdly enough :V

I'm still trying to write that article about how to do CM without using numbers or functions

bolbteppa

Yeah

That Spivak mechanics book in terms of bundles for example

Slereah

It's not easy because the author of that book didn't group the axioms at all

that too

or doing CM as a one dimensional field theory!

There's so much weird CM problems that nobody talks about

like those non-collision Painlevé singularities

and that's just a 5 body problem

Did you know that there's a classical system of infinitely many balls which, due to their collisions with each other, will just exit to infinity in finite time

You have infinitely many balls in your space at $t$ and zero balls at $t + 1$

there's a whole bunch of weird systems like that if you can extract an infinite amount of energy from your system

ACuriousMind

10:38 PM

CM can't even guarantee unique solutions to the equations of motion (cf. Norton's dome)

Slereah

Well those cases are also like that actually

because they are time-reversible

you can have an empty space and then have it filled with infinitely many balls!

hopefully this won't happen to us

ACuriousMind

"False vacuum collpase" got nothing on this

Slereah

Well of course GR has the equivalent problem

ACuriousMind

The universe doesn't end in fire or a soup of entropy, just balls.

bolbteppa

Norton's dome

Norton's dome is a thought experiment that exhibits a non-deterministic system within the bounds of Newtonian mechanics. It was devised by John D. Norton and first discussed in his 2003 paper "Causation as Folk Science". Norton's dome problem can be regarded as a problem in physics, mathematics, or philosophy. It poses interesting philosophical questions about the concepts of causality, determinism, and probability theory. The model consists of an idealized particle initially sitting motionless at the apex of an idealized radially symmetrical frictionless dome described by the equation...

Slereah

10:40 PM

ie nothing prevents our spacetime from just having a random missing point from which cakes pop out

bolbteppa

'While many criticisms have been made of Norton's thought experiment, such as it being a violation of the principle of Lipschitz continuity (the force that appears in Newton's second law is not a Lipschitz continuous function of the particle's trajectory -- this allows evasion of the local uniqueness theorem for solutions of ordinary differential equations)...'

Interesting

Lipschitz in the proof of existence for ode's ftw

ACuriousMind

Sure, if you can sucessfully argue that your forces are Lipschitz then you evade Norton's dome. The problem is that "Forces are Lipschitz" is not a particularly natural assumption

Especially given that the shape of the dome isn't really exceptional. It's hard to explain why a smooth parabola is an acceptable idealized dome but Norton's shape wouldn't be

@Slereah the cake is a lie

bolbteppa

Newtonian Physics is Nondeterministic!!

►

Slereah

The balls problem in GR

The balls problem in GR is a bit different though because you can't really have objects from infinity

Well, you can, with AdS space

but it's rarer :p

More Anonymous

11:26 PM

Hey is there any mod I can ask/plead if its okay to use a big list question?

*question tag

More Anonymous

11:40 PM

Also @bolbteppa u might like this post:
https://www.math.columbia.edu/~woit/wordpress/?p=10533

bolbteppa

@MoreAnonymous make sure to read this rebuttal to it haha

More Anonymous

@bolbteppa i'll have to think about lubos's response but Woit has also shown better understanding of the finer points of string theory than lubos (and its on the internet too) :P

In this whole Woit versus Lubos (sterotypical sheldon)

To be fair Id be willing to put them both on the same stage for the purpose of reality entertainment than science

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