The h Bar

12:00 AM

@StanShunpike That's why I said he probably lost interest.

user54412

@0celo7 Things that are more like collections of results than pedagogical introductions. Lang in algebra, Born & Wolf in optics, and Numerical Recipes in numerics are other things I would call "referency"

0celo7

@StanShunpike He also wrote a 4 volume set on functional analysis, amongst other publications.

ACuriousMind

@StanShunpike He's heard of it, but he didn't pay attention to what it meant ;)

Danu

@0celo7 HAH. I KNEW IT

Books on functional analysis are the hallmark of a true German scientist

0celo7

@Danu Ok...knew what?

LOL

Jimdalf the Grey

12:03 AM

Dang it! I hit "too radical" in this suggested edit but my finger slipped right as I was hitting the reject button and now I've rejected this edit to an answer as an "attempt to reply to the question". That ought to confuse the suggester

0celo7

@ACuriousMind I guess it's time for your first book!

Danu

Yes, talk about spectral theory and Schrödinger operators!

0celo7

A nice 2000 page manuscript on functional analysis.

Danu

KATO-RELLICH!

ACuriousMind

Lol, I don't even really know functional analysis.

0celo7

12:04 AM

@ACuriousMind Devote 500 pages to the spectral theorem.

Beat the crap out of that thing.

user54412

One of my QM professors told us that when his son was born, they didn't have a sturdy table at his home to perform the circumcision. Fortunately, he had a copy of MTW lying around, which was plenty big.

3

Danu

And the One True God: Lieb

@ChrisWhite :D :D :D

NeuroFuzzy

@ChrisWhite That's the best thing I've heard all day

0celo7

How out of date is MTW?

Stan Shunpike

@ACuriousMind That's almost as good as the pun I read on the engineering exchange yesterday about the "dirty" secret by sanitation lines in buildings: engineering.stackexchange.com/questions/443/…

ACuriousMind

12:05 AM

@JimdalftheGrey Isn't that an attempt to reply?

0celo7

Also why has no book since then used that weird honeycomb BS for covectors/tensors/whatever?

ACuriousMind

Ah, I see, no it isn't.

Danu

@0celo7 ??

Jimdalf the Grey

@ACuriousMind I believe the point of an answer is an attempt to reply

0celo7

@Danu Have you read MTW? They have some weird visualization for stuff.

user54412

12:06 AM

@0celo7 It was very cutting edge for its time (including all the 3+1 splitting stuff that preceded numerical relativity and quantization attempts), so it's not too out of date for referencing standard stuff. It doesn't have much causal structure, though.

0celo7

Lemme get a page

Danu

@0celo7 Nope, nope nopenope

0celo7

@Danu There's still hope for you.

@Danu p. 100

@ACuriousMind Why do all the Virasoro generators annihilate the vacuum?

Sofia

@Danu I'll leave it to tomorrow, thank you. Besides that, it makes me nervous when I see again and again questions about many worlds interpretation. From time to time such a stupidity falls into our list of questions.

ACuriousMind

@0celo7 I sure hope they don't.

0celo7

12:12 AM

@ACuriousMind Oh, $n\ge -1$

Danu

@Sofia I, too, have noted a surge in quantum interpretations nonsense

Sofia

@Danu what is "surge"?

ACuriousMind

Unfortunately, "Shut up and calculate" is not yet a close reason.

0celo7

@ACuriousMind Nvm. Bad at reading.

Jimdalf the Grey

@Danu A surge? Really? Seems like a constant river of them to me

Stan Shunpike

12:13 AM

When did "Shut up and calculate" become a catch phrase? lol

Danu

Google definition: "a sudden powerful forward or upward movement, especially by a crowd or by a natural force such as the tide."

Sofia

@Danu but what is "surge"?

0celo7

@ACuriousMind They'd just debate the validity of that statement.

Danu

@StanShunpike Very long ago

0celo7

@StanShunpike My bet's on Feynman.

Danu

12:14 AM

It's a response to 'quantum weirdness'

@0celo7 No

This is popular but wrong

ACuriousMind

@StanShunpike It's a quote variously attributed to Feynman, Gell-Mann and Mermin

0celo7

HSM mod BTFOing me

ACuriousMind

I think it's Mermin who actually said it

Danu

In fact I think Feynman distanced himself from that view sometime in some interview

Mermin from the solid state texxtbook?

@JimdalftheGrey Maybe it's me, then

ACuriousMind

@Danu Yes. I don't know if he subscribed to its content, but it was his response when asked what, in his opinion, the Copenhagen interpretation tells us

Sofia

12:16 AM

@Danu Mermin said what?

ACuriousMind

See Wikiquote for the sourced quote, surprisingly

Danu

@ACuriousMind Wiki saves us all

@Sofia I was talking to @ACuriousMind

@Sofia I am typically engaged in 2 or sometimes even more conversations at the same time here in chat; sorry if it confuses you

vzn

AC nice find. feynman has said it somewhat similarly. might dig up the quote. cant recall exactly.

Sofia

@Danu I met Mermin, many years ago. He wrote something as "Ithaca" opinion on QM, but I don't remember what he had to say. Anyway, he is an solid-state physicist.

vzn

mermin has a lot of really great writing on bells thm.

he wrote a book on it.

with a humorous title.

reminiscent of lewis carroll.

ACuriousMind

12:30 AM

Reading a bit more, it seems Mermin's favourite Quantum Bayesianism is also essentially "Shut up and calculate" with an "Oh, and here's how you should think about probability" appended.

vzn

rats, looked, cant find any quote near that from the feynman wikiquote page.

feynman was [apparently] sort of "agnostic" on the topic of qm foundations/ interpretations. it didnt seem to interest him, but he also didnt reject it as unimportant.

Stan Shunpike

Are Grassmamn numbers a different kind of numbers? You know how we have like the natural numbers, and the rationals, and the reals, and the complex....do Grassmann numbers constitute a new category of numbers?

different kind of number*

vzn

12:45 AM

fyi here is something feynman wrote on the subj of qm foundations/ interpretations. not sure if he has ever even said much at all about bells thm etc in print.

in toy models of QM, 1 min ago, by vzn

> We always have had … a great deal of difficulty in understanding the world view that quantum mechanics represents. At least I do, because I'm an old enough man that I haven't got to the point that this stuff is obvious to me. Okay, I still get nervous with it. And therefore, some of the younger students … you know how it always is, every new idea, it takes a generation or two until it becomes obvious that there's no real problem.

in toy models of QM, 1 min ago, by vzn

> It has not yet become obvious to me that there's no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem.

Danu

@StanShunpike They anticommute

Exterior algebra

In mathematics, the exterior product or wedge product of vectors is an algebraic construction used in Euclidean geometry to study areas, volumes, and their higher-dimensional analogs. The exterior product of two vectors u and v, denoted by u ∧ v, is called a bivector and lives in a space called the exterior square, a geometrical vector space that differs from the original space of vectors. The magnitude of u ∧ v can be interpreted as the area of the parallelogram with sides u and v, which in three dimensions can also be computed using the cross product of the two vectors. Also like the cross product...

vzn

feynmans quote above seems to mirror an old one by plank that seems to ref either the rise of atomic theory of matter or quantum theory.

> A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather its opponents eventually die, and a new generation grows up that is familiar with it. —Plank

note also how closely their comments relate to kuhnian scientific theory.

feynman did say this however (somewhat related to copenhagen interpretation)

> I think I can safely say that nobody understands quantum mechanics. —Feynman

Stan Shunpike

@Danu Right, anticommutes. ab = -ba. I got that! :) something I could understand lol. But I thought commuativity was one of the field axioms. so my question was, does that mean we are somehow altering those axioms? and if so, does that constitute a new kind of set of numbers?

I didn't think exterior algebras had anything to do with the field axioms. Do they?

ACuriousMind

@StanShunpike The Grassman numbers simply aren't a field, they're just a ring.

And the exterior algebra is essentially what the Grassmann numbers are

This is just another point where the physicists insist on using different terminology than the mathematicians

Note that you will never see anyone divide by a Grassmann number, and for good reason - there's no divison operation as the inverse of the exterior wedge, either.

NeuroFuzzy

1:04 AM

There has been a rise of quantum interpretation nonsense. Do you know who's to blame? preposterousuniverse.com/blog/2015/02/19/… (Feb 19)

I probably shouldn't say that because I'm just now in my first (real) quantum class...

ACuriousMind

@NeuroFuzzy He doesn't even refute the objection. He presents not a single, definite proposal of testing MWI or any other interpretation.

And yet, he manages to write in complete and utter conviction that all his opponents are either stupid or willfully ignorant

Just like every other person who's invested in any of the interpretations.

/rant

user54412

In my experience, the people least likely to shut up and calculate are the theoretical physicists themselves

user54412

All of my quantum profs would occasionally start rambling about the incomprehensibility of QM

user54412

And I never could figure out why they were so confused by it

user54412

This is why I don't deal with anything quantum anymore -- it's just too boring in my eyes.

hwlau

1:18 AM

@ChrisWhite You mean the prof are confused??

user54412

@hwlau Not confused about how to do calculations, but confused about "what it all means"

hwlau

Ya, it is always the cases

because it can't be expressed in the classical concept we have

user54412

I don't see why people studying QM get so worked up about ontology, to the point where they convince themselves there's some divine understanding right around the corner. I mean, we don't spend months in Newtonian mechanics worrying about what forces are, and no one in GR asks "what do we mean by a manifold anyway?"

4

Sofia

@ChrisWhite where do you learn? Maybe you had not so good teachers in QM.

ACuriousMind

@ChrisWhite You speak my mind.

pranav

1:22 AM

Hi @all , can anyone help me out with : physics.stackexchange.com/questions/166687/… -- would be extremely grateful ...

user54412

@Sofia Caltech, which has its share of brilliant professors, though is also known for not caring about teaching quality.

hwlau

@ChrisWhite because most people know what is force and manifold by experience already, even thoug h it is not exactly, so there is no explaination

Sofia

@ChrisWhite there is nothing divine there. Can you name whom you call brilliant name?

ACuriousMind

@hwlau But that's just...inconsistent! Why can't they just accept probability the way it is, too?

hwlau

I think you mean accept the wavefunction as physical object?

Sofia

1:24 AM

@ChrisWhite my teacher in QM was Asher Peres. Who was yours?

ACuriousMind

@hwlau See, there we go. What does physical object even mean? Why do people not fight about whether the manifold of GR is a physical object, or the phase space of Hamiltonian mechanics?

The phase space is an especially good example, because it certainly is no physical object, yet it encodes all of classical dynamics

Just like the Hilbert space encodes all of quantum dynamics

No one tries to find ontology in the abstract geometry of phase spaces, but everyone is trying to find ontology in Hilbert spaces. It just doesn't make sense.

user54412

@Sofia Since you asked, I learned QM primarily from Hirosi Ooguri (mathematical string theorist) and Mark Wise (particle theorist).

pranav

Hi , I was working my way through : books.google.co.in/… ---- : how did the book calculate $g(\omega_0)$ ? What is $\Delta\omega$ ? Would be grateful for a reply ...

Sofia

@ChrisWhite Hmmm! In universities, different teachers take this or that course to teach, and not always a topic is taught by the best specialist in it. Probably you weren't lucky. Peres was an international figure in "fundaments of QM".

pranav

I am sorry to be intrusive , but would really be grateful - if someone could help me out :)

0celo7

1:34 AM

@ACuriousMind Implying MWI isn't objectively and manifestly correct.

@ACuriousMind Why are you wilfully ignant?

ACuriousMind

@0celo7 If it was objectively and manifestly correct, that blog post would have contained better arguments ;)

0celo7

@ACuriousMind MWI doesn't need arguments. It's a simple fact.

ACuriousMind

@0celo7 What did they bribe you with?!

0celo7

@ACuriousMind Logic and truth ;)

ACuriousMind

@0celo7 Did you receive the payment yet?

0celo7

1:40 AM

@ACuriousMind Umm...no. It has been promised. Here, I have a receipt!

user54412

"~~Archaeology~~ Physics is the search for fact... not truth. If it's truth you're looking for, Dr. Tyree's philosophy class is right down the hall."

3

0celo7

@ChrisWhite Depending on your brand of philosophy, you could be all about facts too.

Sofia

@pranav what is your problem? About what you need help?

ACuriousMind

Bashing QM interpretations with an Indiana Jones quote. I think I have now seen everything.

pranav

Hi @Sofia , I was trying to solve this problem : books.google.co.in/… --- how did the book calculate $g(\omega_0)$ ? What is $\Delta\omega$ ? Would be grateful for a reply ...

Sofia

1:48 AM

@pranav I could see nothing whatever appears is almost blank pages with some long comment. If you need help about some problem, post a question and explain the problem.

0celo7

@ACuriousMind See?

Sofia

@0celo7 I see you are very interested in the MWI.

0celo7

@Sofia Hardly. I subscribe to shut up and calculate.

ACuriousMind

@0celo7 I see. In the face of such overwhelming evidence, I cannot do anything.

0celo7

@ACuriousMind Good.

@ACuriousMind Holy moley.

1

Q: Given the Wikipedia notion of "arc length", how is its manifestly real "signed variant" to be called and denoted?

I am dissatisfied with the presentation (not to say "definition") of "arc length", in its "Generalization to (pseudo-)Riemannian manifolds", as given in Wikipedia. (Who isn't?. But I'll sketch it here as a starting point anyways.) Namely: [arc] length of curve $\gamma$ as $$\ell[~\gamma~] :...

Sofia

1:54 AM

@0celo7 you, young people don't have ambitions. When smth. is too difficult you give up.

0celo7

250 bounty!?

@Sofia I don't think this has anything to do with my age.

ACuriousMind

@0celo7 That is not the worst bounty I've seen, and that's all I will say to that.

0celo7

@ACuriousMind I have absolutely no clue what this guy is asking!

(Yes I know he's the weird GR user.)

Sofia

@0celo7 Hmmmm! Why we, the former generation are willing to understand the things, and you the young aren't?

0celo7

@Sofia Perhaps your willingness has stretched the limits of physics. Interpretation is up to philosophers, not scientists.

pranav

1:58 AM

@Sofia , the problem is : a ruby laser has the following characteristics : $n_0$ = 1.76 ; $t_{sp}$ = 3 x $10^{-3}$ s ; $wavelength$ = 6943 x $10^{-10}$ m . I need to calculate the gain coefficient of the laser . I first need to calculate the $g(\omega_0)$ ? Also , $g(\omega_0)$ = $\Delta\omega$ ? How do I calculate this . $g(\omega_0)$ is the lineshape function of the laser -- physics.stackexchange.com/questions/166687/…

ACuriousMind

@Sofia Do you have a coherent notion of what understanding means? Quantum theory without any interpretation is able to predict about everything you ever want to predict. Aside from issues like neutrino oscillation, we are able to describe and predict almost every interaction that can ever take place. What more do you want?

pranav

Sofia

@ACuriousMind do you have some notion how to help this fellow that I see that all the time asks for help?

@ACuriousMind and nobody pays attention?

ACuriousMind

@Sofia I have no idea what's going on with lineshapes and lasers. Nobody is replying because they a) don't have time or motivation to help or b) don't know the answer.

Sofia

@dmckee maybe you can give a hand of help. This fellow @pranav asks all the time help. But I am no laser-physicist.

@dmckee how to help?

dmckee

2:02 AM

I can't help him. I don't do lasers beyond turning them on and pointing them where I need the light.

Sofia

@pranav @dmckee who is here a specialist in lasers?

dmckee

No idea.

Sofia

@pranav I advise you to post your question. Now it's late in the night, but tomorrow let's see who can give you some advice.

@ACuriousMind you there! You ask me if I have coherent notion of understanding?!

ACuriousMind

@Sofia Yes. It's not an easy thing to say what it means to understand something, is it?

Sofia

@ACuriousMind shut up and calculate means don't make effort. If something is difficult leave it!

ACuriousMind

2:09 AM

@Sofia No, that is not at all what I take it to mean. It is the viewpoint that only empirical predictions are meaningful, and any underlying ontology is meaningless.

0celo7

@ACuriousMind If $e_i$ is a nonholonomic frame, what is its action on a function?

Sofia

@ACuriousMind I saw once a saying that I liked the nature and its laws lied in darkness. God sayd shall be Newton and it broke light (sorry for the bad English). These were our predecessors. They made light. And what we do? Quote them!

@ACuriousMind understanding requires to work hard and try to understand what's not yet understood.

ACuriousMind

@Sofia But you still haven't told me what it means to understand something. I say we don't need any interpretations for QM because we already understand it in all ways desirable - we can extract from it any prediction we would want to make.

0celo7

@ACuriousMind For $e_i$ holonomic it is obviously the partial derivative.

Is it just some unspecified derivation?

ACuriousMind

@0celo7 I have no idea what (non)holonomic frames are

Sofia

2:15 AM

@ACuriousMind We both understand what means understanding. For all practical purposes we know what's that. Besides, I am an engineer not a philosopher.

0celo7

@ACuriousMind A holonomic basis is a coordinate basis.

Sofia

@ACuriousMind One cannot hide behind words! QM is in a crisis, and the collapse is its name.

0celo7

@Sofia Any crisis is made up by individuals seeking research grants.

ACuriousMind

@Sofia Why? Does collapse prohibit us from making correct predictions?

And, by the way, this is philosophy, and one of the only parts of philosophy I consider worth thinking about - what does it mean to know and what does it mean to understand?

0celo7

@ACuriousMind Ethics is the only truly useful aspect of philosophy.

ACuriousMind

2:21 AM

@0celo7 Ethics is at least one other part I would throw into the trash can, yes, but its usefulness is often overrated. Many people do not follow any coherent ethic in the philosopher's sense and yet manage to be decent human beings.

Mark Mitchison

You forgot about science, the really useful bit of philosophy :)

ACuriousMind

@MarkMitchison Touché

user54412

@MarkMitchison Shhh. Once it becomes useful to others, we're no longer allowed to call it philosophy. ;)

0celo7

@ACuriousMind Still no clue what a (non)holonomic frame is?

Whatever, posted it.

ACuriousMind

Oh, damn, there should be a would not throw in my reply about ethics :D

0celo7

2:24 AM

@ACuriousMind Yeah I figured as much.

Mark Mitchison

@Sofia There is only a "crisis" if you accept realism. So most people prefer not to. "Crisis solved"

ACuriousMind

@0celo7 Well, telling me what a holonomic frame is didn't really enlighten me what a non-holonomic frame is, to be honest :)

Mark Mitchison

@ACuriousMind Didn't even notice, I got what you meant.

I certainly wasn't implying that you forgot to throw science in the bin :)

ACuriousMind

@0celo7 "Not a coordinate basis" doesn't really make much sense to me right now

0celo7

@ACuriousMind Do you even diffgeo? A holonomic frame is a coordinate frame, i.e. can be represented by partial derivatives.

Yes that's my issue.

We can always make one, right? There's a theorem that says so.

Crap

Gram-Schmidt?

ACuriousMind

2:27 AM

@0celo7 Should work, it's just a vector space, after all

0celo7

@ACuriousMind Ah, but what is it really?

What is the manifold?

ACuriousMind

Arrrrrrrrrgh :D

You can start the new field of "GR interpretations". "Relativistic Bayesianism" sounds good, for example. "Many Manifold Interpretation". "The Stockholm Interpretation"

vzn

re (in)significance of QM interpretations. (luvd the raiders of lost ark quote!) its important because QM is potentially incomplete as argued by EPR. an interpretation might help point to a "more complete" theory.

0celo7

@ACuriousMind Quantum fluctuations change the metric slightly. Thus by MWI (proof pending) we create a plethora of universes with slightly different metrics. We then compactify the various universes into a cylinder. Then the quantum field equations are the Navier-Stokes equations, which can be exactly solved using the formalism of quasihomological fractional dimensional affine funtor analysis.

@ACuriousMind This is called the "many manifolds interpetation" (MMI). Boom. Nobel, Fields and Clay in one go.

vzn

so from an experimentalist pov, suppose you had some theory "QM2" that is a subtle revision of QM that can only be detected in very subtle conditions not yet ever set up in the lab. and then you build the experiment that successfully discriminates QM1 from QM2. thats nobel level work. same for the theoretical side.

those that deny such an experiment is possible might not be very much aware of the history of nobel prizes (which basically are an "official" award for kuhnian shifts)

ACuriousMind

2:36 AM

@vzn I do not deny such an experiment is possible. I demand that they actually show me the experiment before making all sorts of bold claims and fighting over which of their indistinguishable "better" theories is "correct".

vzn

and ofc if nobody here wants to ever win a nobel, then carry on & ignore the whole debate as already argued by several :)

ACuriousMind

God, I fail at negations.

vzn

me2 hah

Stan Shunpike

2:51 AM

So I gather LHC has been (or was) closed for like upgrades or something like that the last couple years. Has it been restarted?

ACuriousMind

Well, Wiki says reopening is planned for "early 2015".

0celo7

@ACuriousMind This mode expansion is killing me. The definition of the Virasoro generators is $$T(z)=\sum_{n\in\mathbb{Z}}z^{-n-2}L_n$$ But from the field theory we get $$T(z)=\frac{1}{2}\sum_{n,m\in\mathbb{Z}}z^{-n-m-2}:a_na_m:$$ (cont.)

@ACuriousMind Di Francesco has the solution $$L_n=\frac{1}{2}\sum_{m\in\mathbb{Z}}a_{n-m}a_m\quad n\ne 0$$ $$L_0=\sum_{n>0}a_{-n}a_n+\frac{1}{2}a_0^2$$

How in the world do I verify that?

Stan Shunpike

@ACuriousMind

yeah well that's vague

lol do they usually leave it open

so in case they need to adjust it they can?

ACuriousMind

@0celo7 You plug the formulae for the $L_i$ into the first expression and convince yourself that the second comes out?

Stan Shunpike

I have no idea how the finances work for these kinds of things.

ACuriousMind

2:58 AM

I don't know any "easy" way except just doing the tedious shoveling of indices and sums and trying no to drop anything

0celo7

@ACuriousMind It's the "convincing" that I'm having trouble with.

Argh. I have to move the positive modes to the right, correct?

ACuriousMind

Yeah, I think so. Could also be the negative ones, though, I'm bad at remembering which is which :D

@StanShunpike I think they run the beams and continuously collect data when they're not upgrading, but I'm not sure

Stan Shunpike

Yeah, that's what I've heard too. From what I remember reading, they basically did that 40 years or something in order to find the particle they call the Higgs Boson. I say "they call" because I gather the observed particle could be one of many possible ones and they were reluctant to specify which one initially.

ACuriousMind

@StanShunpike The LHC was first fired up in 2008, so "40 years" is a bit hyperbole ;)

Stan Shunpike

Really? oh well, weren't there other ones though?

ACuriousMind

3:02 AM

Yeah, there are/were predecessors at the same location with lower beam energies and different beam compositions

And they are reluctant to say what they observed because it is really difficult to extract anything from the overwhelming amount of data that comes out of such a collision. You don't see nice blips on a screen and can say "Hey, that was particle X" ;)

Stan Shunpike

Yeah, I gather as much.

The textbooks always make it seem so neat and clean.

But that's really a simplified view of a lot of thought people have gone through to get the facts straight.

0celo7

@ACuriousMind I've convinced myself of the $\frac{1}{2}a_0^2$ :D

Or not. Crape.

NeuroFuzzy

Crepe!

ACuriousMind

Now I'm hungry

A good thing I have chocolate cake.

NeuroFuzzy

I got a text today. "Sardine"

they meant to text "awesome"

but autocorrect happened

ACuriousMind

3:11 AM

Mh, sardines aren't really awesome.

Stan Shunpike

@NeuroFuzzy Famous last words for many relationships.

ACuriousMind

@StanShunpike Sardine? :D

Stan Shunpike

lol "But autocorrect happened"

0celo7

@ACuriousMind Does normal ordering I just put all the positive modes right or the most positive modes right?

ACuriousMind

@0celo7 My definition is that $:a_n a_m: = a_m a_n$ if $m < n$ and the other way round otherwise, so most positive fits better, I think.

0celo7

3:24 AM

@ACuriousMind TFW random zeta function appears

I'm bad at this.

ACuriousMind

@0celo7 You're expecting too much - the "I have no idea what's going on" is completely normal when reading advanced texts. (Partly because they're difficult, partly because physicists regrettably aren't very well trained to communicate their ideas clearly)

0celo7

Perhaps I'm just retarded.

I think I'm doing too much work. Simplify the approach!

We can shift the summation variable in an infinite sum, right?

ACuriousMind

@0celo7 Yep

I'll be off now, gotta get some sleep before the sun rises. :P

0celo7

Then $$\frac{1}{2}\sum_{m,n}z^{-n-m-2}:a_na_m:=\frac{1}{2}\sum_{m,n}z^{-n-2}:a_{n-m} a_m:$$

Thus $$L_n=\frac{1}{2}\sum_m :a_{n-m} a_m:$$

Stan Shunpike

Has anyone here read anything about applications of partition functions to neural systems? I'm just curious whether they actually are useful for biological models.

vzn

3:38 AM

stan re higgs, great documentary particle fever, check it out, anyone else seen it? luvd it

re significance of interpretations, recognize its a minority position, as it has been for decades, as reflected in sentiments in this room. however to "play devils advocate" so to speak its interesting to contrast two recent (starred) quotes by CW

yesterday, by Chris White

There are plenty of people who can ace textbook "regurgitate the information given to you" courses but who lack the creative ability to extend knowledge in ways never before done.

2 hours ago, by Chris White

I don't see why people studying QM get so worked up about ontology, to the point where they convince themselves there's some divine understanding right around the corner. I mean, we don't spend months in Newtonian mechanics worrying about what forces are, and no one in GR asks "what do we mean by a manifold anyway?"

one might argue that copenhagen interpretation aka "shut up and calculate" is the ultimate in "regurgitate the info given to you"...

those that are looking closely at interpretations are in fact attempting to exercise "creative ability to extend knowledge in ways never before done"....

Stan Shunpike

@vzn oooo cool, I'll check it out

vzn

aka in movie metaphors, in star trek "to boldly go where no one has gone before" :)

DanielSank

@Danu Yeah, Szechuan food :)

This is one of my favorite Szechuan dishes.

Also look up any recipe for Szechuan hot pot. You will not be disappointed.

0celo7

3:54 AM

@ACuriousMind I just spent an hour on a single calculation. I hate my life right now.

DanielSank

@0celo7 An hour doesn't sound that bad.

0celo7

@DanielSank I was verifying an equation in the text.

I didn't even do anything productive.

Just stared at some infinite sums for an hour.

DanielSank

@0celo7 Do you understand the equation?

Sounds reasonably productive :D

Give yourself some cred.

0celo7

@DanielSank Hopefully? You a String Theory / CFT guy?

vzn

"interepretations" ≠ "ontology"

DanielSank

3:56 AM

@0celo7 Not a strings person, no.

vzn

DS hows the qm computing going :)

DanielSank

@vzn Great.

I love it.

@Sofia: I looked at the question to which you pointed me. I don't think I understand what the OP is asking.

0celo7

@DanielSank The proof boiled down to showing that the commutation relations of the Fourier modes and normal ordering are entirely equivalent. I had this nasty $\propto\delta_{n,0}$ piece that wouldn't go away. Then I realized $n\ne 0$. I'll rework the proof in Calc tomorrow. I guess that was productive, in a sense.

vzn

cool so DS wouldnt you say the martinis lab is farther along than anyone in the world in qm computing? :) neat to run into someone from it, "small world"

Stan Shunpike

4:22 AM

Is the martinis lab well known? I've never heard of it.

0celo7

@StanShunpike interesting question

2

Q: What is a nongeodesic orbit?

I have read that in the Schwarzschild spacetime for a nongeodesic circular orbit the radial acceleration becomes positive for $r<3r_S$. Intuitively, the acceleration should be negative, pulling the object in. My questions: What does a nongeodesic orbit even mean? Is it a solution to the gener...

general-relativity orbital-motion acceleration

vzn

4:35 AM

hey stan re NNs, try looking into "deep learning/ networks" for latest tech in that area. re qm computing, it is maybe not so well publicized to nonscientists... although there was a front cover Time magazine issue last year or so...

Stan Shunpike

I've heard of quantum computing. I took a class at Caltech on information theory and learned all about boolean algebras. But, in my experience, labs are kind of like a cultural thing. You learn sorta by reading publications and by word of mouth where the hot research is going on. I just had never heard of the martinis lab. It's interesting that they were purchased by google, at least that's what I read.

@vzn I don't know much about deep neural nets. I'll check on it. If I recall, it was that technology that facebook used to design that facial recognition software with 97% accuracy.

@0celo7 That's really cool. What a neat question and answer. Where were you reading about that? Wald?

vzn

caltech eh? nice! are you in college? whats your major? yes deep learning is being used by google, yahoo(?), facebook, etc.

DanielSank

4:57 AM

Guys, you know what would be really awesome: support for a music playlist in online chat rooms.

I'd dig that.

@0celo7 I'm intrigued. Any chance you could spell out the problem? I may not be a QFT guy but I know second quantization and I'm curious about how normal ordering comes in.

Stan Shunpike

6:42 AM

@vzn I was at Caltech. I transferred to the U of C for medical reasons. Yeah college. I'm actually an econ major. But I love physics, I just don't think I want to be a physicist. I actually haven't really taken classes beyond high school physics. Most of what I learned I learned on my own just for fun. If I had to pick a discipline that gets me up in the morning, it's this stuff though. That movie particle fever was really interesting. I've never seen the inside of the collider. It's amazing!

@vzn I actually specialize in biomechanics. I've spent 5 years studying how to treat various musculoskeletal problems using largely Newtonian mechanics. It's remarkable how few serious physicists tackle biomechanics problems.

@vzn Vladimir Ivancevic is one who tried but in my opinion failed. His stuff isn't very insightful, but at least he uses real physics. Most of the physics books on how bodies actually move are remarkably uncreative and, in my opinion, demonstrate no one has really ventured into this territory to make an impact. Perhaps on the engineering side there is more, but certainly the medical practice is lagging.

@vzn the doctor who treated me and I are going to write a paper about our findings. hopefully it will change how people approach these sorts of problems.

I often laugh because my doctor doesn't know physics, so he always is amazed when I use it. But, having studied QFT, Newtonian mechanics seems so simple. I guess though one shouldn't judge an idea by how simple but instead by how powerful it is.

Stan Shunpike

7:04 AM

Fun aside: My high school physics teacher did his PhD with Higgs

books.google.com/books/about/…

Sorry about all the pings btw. new to chat. just realized only one is needed.

Danu

8:55 AM

@ChrisWhite Oh man, impressive! I learned from Jan de Boer, who was also my bachelors thesis supervisor. Together with Verlinde he's the big shot in Amsterdam, but he's not as famous as either Ooguri or Wise

@vzn Saw it, was annoyed by the lack of inside info :\

@DanielSank This'd give rise to massive conflicts, haha

@0celo7 Ah, more misconceptions of self-studying folks <3

@DanielSank Durrrr :P Thanks for the recommendations

@ChrisWhite Wait... you study astro @ Princeton?! Did we already have this conversation? I spent about a month in the basement of the astro department in Januari of 2014, haha

Working with Daan Meerburg & Enrico Pajer (who is now on tenure-track in Utrecht) on certain models of inflation

It was a nice, hard-working time ^^

alarge

9:52 AM

@StanShunpike Well you can use stat mech to model some patterns of the brain if that's what you mean. There are also a lot of other connections between neural networks and stat mech.

0celo7

10:30 AM

@StanShunpike Straumann.

Awake at 5:30. I hate my dog.

Danu

@user12262 I am kind of happy to see that it seems the leading answer to your question essentially says what I was saying :)

@0celo7 lol

bolbteppa

@ACuriousMind this math.stackexchange.com/questions/1163032/… is the question I was trying to ask you on here about two weeks ago :D

0celo7

@Danu You keep saying self-study like its a bad thing. It's not like I can do any other kind of study right now.

Holy crap now my cat wants food.

Danu

@0celo7 No it's good and impressive

you guys just develop a few funny notions in the process :D

0celo7

@Danu My psychology teacher gave up trying to learn QM.

I'm gonna finally have my copy of Shankar back

Danu

10:47 AM

Hahaha

A brave attempt, I am sure

0celo7

@Danu I knew it was over when I had to teach him matrix multiplication

Danu

@ACuriousMind @ChrisWhite and others, I made some statements yesterday about the (lack of) availability from the Springer website of the book 'Topos of Music' by Mazzola. I have discovered that I was wrong: link.springer.com/book/10.1007/978-3-0348-8141-8 is where I was able to obtain a free, legal copy (using my 'university access', of course)

0celo7

-

Danu

@0celo7 Yeah... probably way over his/her head mathematically

0celo7

Applications of Lie groups to diff eqs?

Sounds cool, but I'll never read it :/

Danu

10:54 AM

Me neither, probably

0celo7

I can't paste into the chat.