The h Bar - 2019-01-08

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Sir Cumference

00:04

Why is word crashing when I try to copy a sentence ;-;

enumaris

it doesn't like you

Sir Cumference

@enumaris I like to imagine it's microsoft's way of punishing mac users

enumaris

how much memory would a 4million x 256 x 300 matrix take...way too much right...

like 500 gigs?

1.2 terabytes?

for 32bit floats...

ouch

that's...gonna take forever to train on too...

hmmm

Secret

00:25

JohnRennie is on quantamagazine?

enumaris

at him

tho the picture doesn't really look like his profile pic

danielunderwood

00:46

@enumaris are you trying to stick your entire training set in memory or something?

NormalsNotFar

01:30

According to the Helmholtz decomposition theorem, one can decompose a vector $V_a$ into transverse and longitudinal components: $$V_a=V_a^{\perp}+V_a^{\parallel}$$ where $\partial^aV_a^{\perp}=0$ and $V_a^{\parallel}=\partial_a \varphi$ for some suitable $\varphi$.

Can the same be done for higher order tensors? E.g. can we write some symmetric tensor $T_{ab}$ as $T_{ab}=T_{ab}^{\perp}+T_{ab}^{\parallel}$ where $\partial^aT_{ab}^{\perp}=0$ and $T_{ab}^{\parallel}=\partial_{(a}\varphi_{b)}$ for some vector field $\varphi_a$ ?

1 hour later…

Secret

02:40

7

Q: How can one obtain the metric tensor numerically?

I am self-studying General Relativity. Is there a method for obtaining the metric tensor exterior to a specified mass distribution numerically? In the simplest case of a spherical mass this should yield the Schwarzschild exterior geometry. I am primarily interested in such cases, without radiat...

general-relativity metric-tensor computational-physics simulations

Some really excellent material here

enumaris

03:08

@danielunderwood at that rate I can't even put it in storage lol

2 hours later…

user351417

04:53

@Secret Looks like a different person: en.wikipedia.org/wiki/John_Rennie_(editor) :P

John Rennie

05:22

@Secret It wasn't me, I wasn't there and anyway you can't prove a thing.

1 hour later…

rob

06:32

@Secret Huh, I met that guy once. I hadn't thought about him in years. He gave a talk to a small audience, probably a college honors society induction ceremony in 2001. I remember he gave off a vibe of "only science can ever be right" which I found off-putting, and I blamed it on his prominent position as a magnet for correspondence from really crazy people. Scientific American (his magazine then) had just devoted an entire issue to debunking a book called "The Skeptical Environmentalist."

Looking back from the era of fake news, the whole memory is rather quaint.

1 hour later…

Avnish Kabaj

07:52

user image

Slereah

08:34

You know

one thing I should make for my website is

A thing to compute tensor quantities online

It would be practical

Anonymous

@AfterShave It is. But you'd have to be lucky for someone to know the material and take interest in your question and answer it. :P

Wang Yun

09:46

Do anyone know that how to calculate the Lagrangian of quantum harmonic oscillator?

Slereah

what do you mean by "calculate the lagrangian"

The Lagrangian is typically given in a theory

Do you mean get the Lagrangian path integral from the Hamiltonian path integral

user2723984

@WangYun given what?

Wang Yun

sorry,my fault

I mean, I wnat to know the form of the Lagrangian

then I could calculate the oscillator's action

Slereah

It's a harmonic oscillator

So harmonic oscillator Lagrangian

$$L = \frac{m}{2} (\dot{x}^2 + \omega^2 x^2)$$

or somesuch

Wang Yun

Is $x$ a function of $t$?

like classical mechanics?

$x=Asin(\omega t+\delta)$ ?

Slereah

09:57

yes

Although beware that you don't actually use the lagrangian in canonical QM

You only use it in path integral QM

Wang Yun

I know

Slereah

but you can compute the action for that yes

Result is in Feynman Hibbs, it's solvable in closed form

Wang Yun

My teacher asked me to calculate the action of harmonic oscillator

when learned propagator

Slereah

you can take a look at Feynman Hibbs for all that yeah

it's a good ressource on it

Wang Yun

so I just do the calculation for the action like classical mechnics ?

Slereah

10:02

Yes.

Wang Yun

Thank you man

BTW, please forgive my poor English

Slereah

The action of $(m/2) (\dot{x}^2 - \omega^2 x^2)$ is $$S = \frac{m\omega}{2 \sin(\omega T)} [(x_a^2 + x_b^2) \cos(\omega T) - 2 x_a x_b]$$

if you need to check

www2.oberlin.edu/physics/dstyer/FeynmanHibbs/Prob2-2.pdf

there's a proof

Wang Yun

OK

user2723984

A minor question for the mods: is there any reason for which the "similar question" list to the right of the text field when asking a question doesn't automatically open links in a new tab, while the "question that may already have your answer" does? Actually, why are there two separate lists for that?

Anonymous

10:47

@user2723984 It seems like a bug. You can raise it on Meta!

Anonymous

By the way, there's no reason to direct your questions towards mods. Neither mods nor normal users have complete knowledge of reasons behind specific UI feature implementations. Only the SE developers would have that. We only know what's shared publicly and through the mod-channels. The best place to ask site-related issues is Meta. Although, of course, it's not a bad idea to ask in here first.

Anonymous

> Actually, why are there two separate lists for that?

Anonymous

I guess the "Questions that already may have your answer" list only shows you questions with similar tiltles. Whereas "Similar Questions" list shows you questions with similar question bodies + titles + tags.

user2723984

@Blue I think it's an issue specific to physics SE, not the whole site, because for example mathSE doesn't have those two lists

Anonymous

11:04

user image

user2723984

not true, it appeared after a while

Anonymous

@user2723984 All SE sites have them, as far as I know.

user2723984

it seems like quite a basic thing not to have been raised a zillion time on the main meta

-11

Q: Have all links open in a new tab?

Possible Duplicate: make links posted by users open in a new window When I follow a link in a question on any question/answer on S[OUF] it doesn't open in a new tab. I think it should. I'm not a big fan of having to use the back button and wait for a page to load all over again. Why do...

feature-request status-declined

lol it's a different issue, but it's the same principle and it doesn't look like it was well received

comment with 9 upvotes: "Learn how to use a browser. I suggest SuperUser for your question."

Anonymous

@user2723984 Doesn't harm to drop in the Tavern and ask whether they have duplicates. If not, make a new thread. ;)

Slereah

11:55

know what I hate?

Naturalness

that's such a silly notion

user2723984

@Slereah Have you read "lost in math" by Sabine Hossenfelder?

Slereah

I did not

user2723984

do

John Rennie

@user2723984 I have ...

user2723984

I just finished the audiobook (because only time I have to read is when I walk)

I found it utterly depressing, but interesting

@John Rennie what did you think of it?

John Rennie

12:00

The book is giving you one person's view, and that person has a rather cynical view of life. The reality is that you don't tell top physicists what to do - you give them the funding to do what they want (actually they'll do what they want anyway :-).

Slereah

Also give me funding plz

user2723984

yes, I'm aware that a single person's opinion is not the whole story, but her arguments were pretty convincing (if a little repetitive)

"The reality is that you don't tell top physicists what to do - you give them the funding to do what they want (actually they'll do what they want anyway :-)." is exactly the reality she depicted

Slereah

Most arguments are convincing

John Rennie

@user2723984 And that's the way it should be. If you go to the doctor you don't tell the doctor how to diagnose you, you assume they know how to do their job better than you do.

Slereah

That's why people believe them

The hard part is making sure they're true

user2723984

12:04

@JohnRennie does that make all arguing about the way to research physics pointless? After all, the author is a physicist too, not a layperson with some misguided opinion.

John Rennie

Hossenfelder also misrepresents what naturalness means. For more on this read this article or this rather longer article.

Slereah

What, no Motl article?

John Rennie

@Slereah Motl is a little too rabid for my taste :-)

Slereah

The whole naturalness argument is a bit silly to me

I mean if you find a theory that both work and is more natural

by all means

But I don't think lack of naturalness is any flaw of a theory

Can't tell the universe what to do

John Rennie

@user2723984 the basic problem is that physics is an experimental subject. A theory is just maths until it is tested by experiment. And right now we don't have the experimental data to test new theories.

But if you just fire all the HEP theorists then when the data comes in we won't have the skills to figure out what it means. So you pay the HEP community to keep their skills sharp by whatever means they prefer in the hope that when the data comes along progress will be quick.

The HEP community costs nothing compared to the big experiments like the LHC and LIGO, so I don't have a problem with funding them to keep bashing away even though 99% of what they do is probably wrong.

user2723984

12:09

ah yes sure, I don't think anyone suggests firing all HEP theorists. The book is merely a critic of the methods used for theory assessment in absence of experimental data

knowing that "theory assessment in absence of experimental data" might be an oxymoron

Slereah

Honestly I don't really care that much about assessing theories

I just think it is fun

user2723984

experimentalists still have to know where to look

Slereah

but I suppose the people giving out grants want results eventually

"I need answers! I need them now or I need them eventually!"

John Rennie

@user2723984 precisely. Hossenfelder and the other arch-cynic Woit take the view that it's useless to pursue theories we can't test. I think they are being very short sighted. We know it's probably useless to pursue theories we can't test but we do it anyway to keep building the skills needed for when we do have that data.

Slereah

I'd say it's not useless to pursue theories we can't test

user2723984

12:13

do you have a suggestion for a book that takes a less extreme point of view?

I mean I could read Greene's elegant universe to balance things up

John Rennie

Greene's book is rather dated these days, though it's still an enjoyable read.

user2723984

but as far as I understand is the opposite extremum

John Rennie

The problem is that iconoclastic books generate lots of publicity and sell well. People don't write books saying "it's all OK keep going" because they won't sell.

user2723984

makes sense

bolbteppa

@user2723984 you should read the whole comments section here:

Slereah

12:16

@JohnRennie You should read "Lost causes in physics"

It's the opposite of iconoclastic and it's hilarious

bolbteppa

backreaction.blogspot.com/2018/12/…

You get a sense of how shocking her viewpoint is

When challenged by someone who knows what they're talking about, you see the cracks

John Rennie

@user2723984 Greene's book is enthusiastic but it's very different from Hossenfelder's book because it wasn't written as a polemic. It's Greene's attempt to share what he knows and loves with the interested amateurs. Hossenfelder appears to no longer love what she does, which is a shame really.

@Slereah this book?

Slereah

That's the one

That's the physics book with the biggest axe to grind I've ever read

It even mentions Motl

bolbteppa

amazon search doesn't give any results for Motl

John Rennie

Available free here

I assume that's kosher since it's the ResearchGate site

bolbteppa

12:21

“Science is not that easy.”
Lubos Motl

That's all it has

John Rennie

user image

Huh? :-)

Slereah

@JohnRennie I told you it's great

There's a whole chapter about infant death, too

which is quite probably the least likely subject I've seen associated to quantum mechanics

It's all entirely serious physics, though

just very weird parallels

(basically the thrust of all the weird chapters is to explain that poor understanding of probabilities leads to poor understanding of QM)

not made easier by the fact that QM uses a special probability theory

1 hour later…

tarit goswami

14:04

I am not getting what is the problem while passing light through polarizer if we think light as photon particle. Can anyone tell me?

Nick

14:47

I think the point of the polarizer is to show light has a duality, you can constrict the motion of the particle through only one plane and such.

Yong's double slit wouldn't show diffraction (in the way we see it) if light were simply particles

Even if you imagine a bunch of tiny balls through a polarizer meant for wave light, you'd still have changed that system which was entering into the system that leaves. I'm not sure if that mechanics is worth studying though.

John Rennie

15:28

Ah, the HNQ. A wonderful feature :-)

Slereah

15:41

Can you actually detect if the universe got mirrored through parity properties, though

like what kind of experiment would differ

I'm not 100% sure

Sir Cumference

Wouldn't a difference on the microscopic scale have an overall affect on the macroscopic scale?

Slereah

probably not in any noticeable way

Parity violation is pretty rare anyway

rob

A great read on the subject (which has aged surprisingly well) is Gardener's "Ambidextrous Universe." Decades ago I read a short story whose premise was that an un-reflected individual awoke in a reflected universe, and [spoiler] slowly starved because all the proteins in his food had the wrong chirality. I haven't been able to track it down, though. The last time I tried I wound up writing this Physics answer about mirror symmetry, electroweak interactions, and biology instead. — rob 14 secs ago

Nick

16:15

@rob omg

bolbteppa

user image

enumaris

weez

Jake Rose

Wow

my amperes law question got 1000+ views overnight

wtf

that was random

enumaris

16:34

yes indeedy

John Rennie

16:54

@JakeRose it's on the hot network questions list. That always attracts a lot of attention.

Nick

@JakeRose best of luck to you :)

vzn

@user2723984 hi, just finished hossenfelders book recently & we had some discussion in here. shes a lightning rod bordering on iconoclast. the book is very much in line with 2 others that critiqued string theory a decade ago, Smolin and Woit. feel her book is well written/ researched, humorous, and career-risking. she burns bridges, torches groupthink, goes out on a limb due to her conscience which is sometimes a rare quality in humans/ professionals. Bell/ Bohm are other examples in this light.

Anonymous

@bolbteppa Heh. I didn't know that one. :D

2

Jake Rose

17:20

my lecture notes say

imagine a complex voltage on some component $V=V_0 \exp(\omega t - \phi)$ and a current flowing through it of $I=I_0\exp{\omega t}$

then the phase shift of the current is locked up in the $I_0$ right?

@JohnRennie how do you get on the hot network questions list?

John Rennie

@JakeRose the algorithm that determines what questions go on the HNQ is a closely guarded secret, presumably to stop the SE members from gaming it.

Anonymous

@JakeRose I don't know what you mean by "locked up".

John Rennie

I have to say that whatever the algorithm is, it makes some very strange choices at times.

Anonymous

@JakeRose You missed the iota's ($i$'s) there, in the exponentials.

Jake Rose

@Blue nothing mathematical. Just how I speak

Anonymous

17:26

@JakeRose Okay, but I don't really understand the question.

Jake Rose

oh yes I see sorry

the phase in the current term is in the $I_0$ I.e. it is complex and of the form $I_0 = A\exp(i\theta)$

Anonymous

@JohnRennie It's pretty easy to game it though. Just write a catchy title and something popular-science-y so that it gets a lot of clicks in the first few hours. :P

John Rennie

@JakeRose the voltage and current have a phase difference of $\phi$. But I wouldn't say the current is phase shifted or the voltage is phase shifted. All you can say is that have a difference relative to each other.

Jake Rose

Oh

I see

The current is what we’re relative to

Anonymous

@JakeRose Nope, not necessarily. $I$ can just as well be written as $I_0\exp(i(\omega t-\phi))$, considering $I_0=V_0/|Z|$.

John Rennie

17:32

The phase is just the argument to the complex exponential, so the phase of the voltage is $\omega t - \phi$ and the phase of the current is $\omega t$. Subtract these to get the phase difference, which is $\pm \phi$ depending on which way round you do the subtraction.

ACuriousMind

I just noticed I'm 21 upvotes away from earning the golden quantum-field-theory badge. That'd be the first gold badge I have but @JohnRennie has not :)

vzn

@JohnRennie kind of understand what youre saying (theorists are cheap to pay?) but isnt LHC tightly coupled with "HEP community"...? seems HEP is not so cheap if one considers LHC as an intrinsic part of it.

Anonymous

Usually, we write currents and voltages in terms of RMS currents and RMS voltages, or peak currents and peak voltages. In certain contexts, the phase term is "locked up" in the amplitude, but that's not always the case.

Jake Rose

@

I see guys thanks

John Rennie

@ACuriousMind I would comment that I can't get the qft badge because I know sod all about qft. However this didn't stop me getting the GR badge :-)

user2723984

17:35

@vzn I find it curious that the term "iconoclast" pops up so frequently in discussions about this kind of books, especially in a scientific context

John Rennie

@user2723984 iconoclasm sells books. Everyone secretly loves to see the establishment get egg on its face.

vzn

@user2723984 science has some aspects of a "belief system". even supposedly mainstream physicists can have "heretical ideas". science has a social/ community component... its practiced by humans... hossenfelder is nearly writing as a specialist sociologist or anthropologist. hossenfelder is writing for the ages. she will look a little crazy in the short term and a little bit prescient/ "prophetic" in the long term. the "long term" range might even be, after her lifetime.

user2723984

yes sure, but doesn't very fact of science having icons justify clasting them? Having icons is a natural social effect, but one that scientists should try to avoid I think

vzn

@user2723984 icons are part of being human. yes science tries heroically to avoid having icons but yet cant entirely succeed. highly recommend the book "what is real" by Becker, its a nice counterpoint to Hossenfelder, just finished it. by the way (re "less extreme pov") Weinberg parodied by Hossenfelder has a book "dreams of a final theory"... etc...

John Rennie

@user2723984 scientists are human (even though experiment might suggest otherwise :-)

ACuriousMind

17:41

@user2723984 I think the importance of icons (i.e. specific, singular scientists) to the progress of science as a whole is usually greatly exaggerated in popular writings. Sure, successful scientists get a certain amount of reverence and leeway, it's humanly impossible to entirely avoid that. But the "iconoclasts" have to overstate their case rather forcefully in order to really feel like they're clashing with "the establishment" instead of just somber scientific consensus.

bolbteppa

The idea that there is an 'establishment' in science as though it's some cabal is like saying the best known version of the truth is just establishment spin

ACuriousMind

In some cases, the targets are at fault themselves, though. If string theorists didn't try so hard to push the "one true theory" angle in public, they wouldn't be such easy targets. In the end, string theory is such a tiny part of theoretical physics that the amount of diatribes written against it is certainly disproportional - but so is the amount of laudatios

vzn

was looking up this term recently after Secret asked me about Jung. yes even scientists have a version of "consensus reality"... en.wikipedia.org/wiki/Consensus_reality in physics the word for it is "standard model"...

enumaris

I pay my monthly dues to stay inside the "establishment"...at our monthly meetings we mostly mock string theorists by eating tons of spaghetti

2

John Rennie

Nope. The Standard Model is an experimentally tested theory not any form of consensus reality.

ACuriousMind

17:44

On the other hand, if you're not a borderline mad scientist thinking they're gonna discover the secret of the universe, you're not going to spend decades of your life chasing speculative theories, so there's certainly some amount of selection going on there.

bolbteppa

Spaghetti rings or open strings?

Lasagne night could mock brane theorists

ACuriousMind

Take that, M-theory! ::stuffs entire lasagna into mouth, Garfield-style::

enumaris

:D

John Rennie

> tons of spaghetti

You must have excited spaghetti. The ground state of strings is massless.

enumaris

something something E=mc2 something something

ACuriousMind

17:48

@JohnRennie Gagh?

That's what I imagine under "excited spaghetti"

vzn

← :o lol, huh? string theorists as "borderline mad scientists"? wonders if ACM is currently under hooch influence :P

user2723984

Anyway, probably my subconscious took that book as an excuse to console me for not being smart enough to do HEP theory. It worked!

ACuriousMind

@vzn I just came back from work. Draw your own conclusions :P

vzn

it seems that woit + smolin + hossenfelder might all agree on the point that some highly speculative physics is "borderline mad science"... some of the contention is only on where the exact boundary is drawn...

ACuriousMind

Please do not interpret my statements as derogatory - the line between madness and genius is in this case mostly whether you succeed or not.

vzn

17:54

it does seem its getting harder to succeed at being a mad scientist...

ACuriousMind

I agree with critiques of string theory and other theoretical physics only in so far as that many proponents hopelessly overstate their case, but I do not agree with any sentiments that such theories should not be pursued.

John Rennie

@ACuriousMind people eat these - admittedly they usually cook them first

enumaris

It's not determined by how many world ending WMDs you build? I thought...I thought that was the criterion

ACuriousMind

@enumaris You're confusing mad scientists with mad engineers

vzn

Dr strangelove...

enumaris

17:57

sounds legit

ACuriousMind

@JohnRennie I'm thinking very hard about whether or not I want to click that link :P

bolbteppa

If people listened to the iconoclasts, a gigantic mystery theory which is still being discovered would just be thrown away and ignored, the only theory in history to deal with GR's non-renormalizability in any real sense, they would then just as easily flip to defenders of it being studied once that happened

user2723984

@ACuriousMind you'll never look at strings the same way

John Rennie

@ACuriousMind in the UK people eat elvers, though again generally cooked. Traditionally the elvers are thrown live into the cooking pot.

ACuriousMind

::googles 'elver'::

John Rennie

17:59

Baby eel

ACuriousMind

Ah, it's eels

user2723984

@bolbteppa but I don't think Hossenfelder suggests to just tell theorists to pack their things up and go home. She points out flaws in the current state of theory and of research in general, but she doesn't say to just abandon it all.

John Rennie

@user2723984 no, she just says abandon the things she disapproves of. Which happen to be the most interesting areas to work on.

vzn

@user2723984 she has concrete suggestions at the end. shes right about a lot of things. shes partly questioning Big Science and it needs it. one should spend money wisely, esp large amts of it. "Billions" reasonable people can disagree about funding priorities. not every physics/ science funding dollar is well spent... she has a point about very expensive experiments that return null results etc...

ACuriousMind

Man, we're not doing science to be cost-efficient.

user2723984

18:03

But that's sure what it looks like

since every attempt has to promise tangible results to be funded

John Rennie

@user2723984 you've never written a grant application, have you? :-)

ACuriousMind

@user2723984 You...might have the wrong idea about what "tangible" means there

user2723984

ah, no, just as I feared my inexperience is making me talk nonsense

I'm sorry

ACuriousMind

In theoretical physics, you certainly get funded e.g. for investigating things whose "tangible benefit" is making clear some theoretical connection between two other purely theoretical things.

vzn

@user2723984 some ppl rejecting Hossenfelder havent read her. etc big credit to you for actually reading a book about (difficult!) science :)

enumaris

18:06

I have never written a grant application either mmmhm

ACuriousMind

Look at most things Witten has ever written. - he's one of the foremost theorists today, but you'll be hard pressed to find material benefits to most of his work. The abstract/intangible benefit for our understanding of modern theory, however, is immense.

user2723984

@ACuriousMind no don't get me wrong, I understand that

vzn

← was just about to cite Witten in the "mad scientist" theme :o

user2723984

I wasn't talking about completely material stuff

ACuriousMind

We've been here before:

Jul 29 '16 at 15:32, by ACuriousMind

Regardless of whether science has pratical usage or not, it's simply not done for that practical benefit. The artist doesn't create art because he wants to sell it, the musician doesn't play because people will give him money, the philosopher doesn't write books because they will be sold and the scientist doesn't investigate nature because it will be useful. No one stands at the LHC and thinks "I can't wait till we make that accidental discovery that will have practical applications"

user2723984

18:09

but the impression I got from Hossenfelder and other voices is that to be taken seriously you have to promise a lot, maybe more than you could actually promise, but again, I've never done research myself.

ACuriousMind

@user2723984 That may be true but if it is then it isn't unique to any particular subfield - almost everyone is, shall we say, "optimistic" about the impact of their research on grant applications :P

John Rennie

@user2723984 there's a degree of truth to that, but both the scientists and the funding bodies know grant applications paint a rosy view of the potential outcomes.

user2723984

no, exactly, her critic is more general, especially at the end

this is true also for humanities, that have to somehow try to justify their concrete usefulness, which is not the point

vzn

@user2723984 physics seems to be at some kind of crossroads, Hossenfelder senses/ emphasizes it, others do too. even with Higgs, a brilliant finding, LHC is a (very expensive!) "mixed bag"... etc... "time will tell"

Anonymous

@user2723984 I wonder how grant applications from the philosophy departments look like. :P

ACuriousMind

18:14

@user2723984 There's certainly something wrong with the general framework of modern academia. But I think it is less the fault of specific people and more something like a local extremum - the number of people who would need to simultaneously change their ways in order to achieve a better state is too large for change to be easy or gradual.

user2723984

@ACuriousMind reading the message you quoted, I couldn't agree more, I was talking about theoretical applications, not practical. I begun studying physics after having watched too many youtube videos about string theory.

@ACuriousMind and the framework of modern academia, at least from the outside, looks like the framework of everything else - it has to have a measurable output, the funding will be proportional to that

ACuriousMind

I didn't say that there wasn't also something fundamentally wrong with capitalism ;)

enumaris

By the beard of Adam Smith, I doth declare thee commie scum

user2723984

quietly lowers left fist

ACuriousMind

Thanks, McCarthy.

bolbteppa

18:18

*invisible left fist

ACuriousMind

Silence descended as everyone pondered where they would be when the revolution came :P

bolbteppa

'There are various other candidates for a theory of everything, eg Alain Connes' noncommutative geometry, Asymptotically Safe Gravity, causal fermion systems, E8 theory. The statement that M-theory is the only candidate isn't only misleading, it's plainly wrong.' twitter.com/skdh/status/935567322231791617

user2723984

nah, I realize that if I chat instead of studying I might be talking nonsense for the rest of my life

ACuriousMind

@user2723984 A wise realization :)

bolbteppa

When you realize she is calling Lisi's E8 laughable laughable nonsense an alternative, or Connes non-commutative geometry an alternative (that failed at predictions in the LHC), you can only realize how unbelievable her claims are

user2723984

18:26

@bolbteppa ugh, she has her own quote in a huge font near to her photo, that certainly lowers her credibility

bolbteppa

This causal fermion stuff, another highly questionable concept

enumaris

but it's fermions

and causal

ACuriousMind

I remember trying to read about them when a question asking about them appeared here

bolbteppa

When your alternatives are this laughable, and so much time is spent criticizing theory X based on the apparent existence of alternatives, iconoclasm is really the only way to make sense of it

ACuriousMind

Didn't make much sense to me, but then again I don't know how much sense string theory would've made to me if I'd just grabbed a random foundational paper and tried to read it.

Pedagogy is important, but unfortunately most researchers are not good pedagogues

enumaris

18:32

that's why one must be a great autodidact

finally an excuse to use that word

vzn

@bolbteppa you forgot the fluid paradigm :) :P

bolbteppa

@vzn that's not even wr...

:p

vzn

← not even wrong™ :P

bolbteppa

18:50

I mean really, imagine calling this E8 stuff an alternative with a straight face?

enumaris

straight face E8 stuff is an alternative

bolbteppa

Woah

Obligatory

motls.blogspot.com/2007/11/exceptionally-simple-theory-of.html

@user2723984 the paper described in that ^ article is what she's calling one of the 'alternatives'

user2723984

yeah I don't know about that. Even when she described this guy at the Hawaiis on the beach developing theories of everything I was a bit skeptical. Her claims about academia might be more valuable than those about physics.

bolbteppa

That's the Hawaii guy's theory in that link

user2723984

yes, I remember it and I would have inferred it from the very subtle humor of the first figure of the article

bolbteppa

19:03

user image

user2723984

exactly that

bolbteppa

I don't know when I'll get tired of laughing at this whole thing

She let him write a guest post a few weeks ago backreaction.blogspot.com/2018/11/… the guy who wrote the paper tearing up his idea posted in the comments ("decade"), oh man it's just so funny

user2723984

in the book though, she doesn't make particular claims about the theory IIRC, and I didn't get the feeling she was taking it very seriously either, that tweet is weird

bolbteppa

She gives him a privileged position in the book, I mean...

vzn

@user2723984 Hossenfelder visited Lisi in hawaii and stayed as a guest at his house while interviewing him. its a semi hilarious vignette. one of my favorites in the book. + think her account of him is quite empathetic/ humanizing.

tarit goswami

19:29

Suppose $\Psi(x)=\alpha\psi_a(x)+\beta \psi_b(x) $. We have output of some observable in $\psi_a(x)$ state(when it was individual) '$a$' and in $\psi_b(x)$ it was '$b$'. Now if we want to measure that observable in $\Psi(x)$, theory stating we can get either of $a$ or $b$ as output, probability of getting the output $a$, $P_a\propto |\alpha|^2$. My question is how we are saying this? Is this experimental fact?

Anonymous

The Born rule (also called the Born law, Born's rule, or Born's law) formulated by German physicist Max Born in 1926, is a law of quantum mechanics giving the probability that a measurement on a quantum system will yield a given result. In its simplest form it states that the probability density of finding the particle at a given point is proportional to the square of the magnitude of the particle's wavefunction at that point. The Born rule is one of the key principles of quantum mechanics. The Born rule states that if an observable corresponding to a Hermitian operator ...

tarit goswami

@Blue Thanks :) after a long time, nice to see you as a moderator :)

Anonymous

@taritgoswami Heh, thanks. I'm seeing you here after a long time too!

tarit goswami

@Blue Yeah I was busy for exam and now doing internship

Anonymous

@taritgoswami Cool! BTW here's a related question: Born rule and unitary evolution.

tarit goswami

19:43

@Blue Thanks again :)

Anonymous

@taritgoswami I couldn't answer the "Is this experimental fact?" part. It most probably is...but I'm not very sure of the historical aspects of Born's rule. In regular QM it's just an axiom.

tarit goswami

@Blue If it is an axiom then it need to be observation from many experiments I think

Anonymous

@taritgoswami But did they direct test for Born's rule or did they experiment for something else and Born's rule turned out to be a corollary? I'm finding it pretty hard to imagine an experiment to directly test Born's rule.

Anonymous

9

A: Born's Rule, What is the Reason?

Suppose you want to describe the quantum mechanical behaviour of a system, building from scratch the wave equation it should satisfy. Consider first the diffraction pattern obtained with a double slit by a monochromatic light beam and compare it to the one by a monoenergetic beam of electrons. I...

Anonymous

> This also gives one justification for why the Born rule can't involve some other even power of the wavefunction -- probability wouldn't be conserved by the Schrödinger equation.

Anonymous

19:50

Hmm.

Anonymous

The extension to "electron waves" is of course a wild guess that then proved to be true. I would argue that the extension to electrons follows from the fact that electrons couple to electromagnetic waves: physics.stackexchange.com/a/73388/4552 — Ben Crowell Aug 8 '13 at 20:18

enumaris

where tf is my offer

legit this guy is taking forever

grrrrr

Anonymous

@SebastianHenckel: This is not completely thought out and may be wrong. But suppose that the rule for electrons is not the Born rule but a rule saying that probability is $\propto|\Psi|^p$, where $p\ne 2$. If you scatter an EM wave off of an electron, they interact through some wave equation such that the scattered part of $\Psi$ is proportional to the amplitude of the EM wave: amplitude is proportional to amplitude. But then the electron is acting like a detector, and $p\ne 2$ means that the probability of detection isn't proportional to the probability that the photon was there. — Ben Crowell Aug 8 '13 at 21:08

Anonymous

Ah, this is interesting.

enumaris

20:09

sentiment analysis basic test model running mmmhm

tarit goswami

@Blue I will reply back after getting a better understanding :p

Anonymous

@taritgoswami Okay, so this Wikipedia page seems to give some experimental and theoretical motivation for the Schrodinger equation, from classical electromagnetism. And then there's this answer:

Anonymous

3

A: Born's rule and Schrödinger's equation

Indeed, in non-relativistic quantum mechanics, the equation of evolution of the quantum state is given by Schrödinger's equation and measurement of a state of particle is itself a physical process and thus, should and is indeed be governed by the Schrödinger's equation. Indeed, people like to p...

Anonymous

I mean this seems the more natural way to discover Born's rule than the other way round. It should quite difficult to experimentally verify that the exponent should be exactly $2$ otherwise.

Anonymous

My knowledge of the history and experimental aspects of QM is embarrassingly bad. :/

tarit goswami

20:15

@Blue Somewhere I read, it is not a good way to read QM through historic development of QM. It's very confusing :p

Anonymous

@taritgoswami Yeah, I always liked the mathematician's approach to QM --- they don't need to worry about experiments and history. :P

Anonymous

The history of QM seems more like a puzzle, which they put together in bits and pieces, rather than a logical chain of events. I guess classical electromagnetism was a huge motivation for it too, since it was already tried and tested.

tarit goswami

Good night @Blue , bye for now

Anonymous

20:36

Oh nice, Born's original paper is available in English: neo-classical-physics.info/uploads/3/0/6/5/3065888/….

enumaris

21:01

oh nice, the algorithm actually overfit on the training data

fun times

I'm not sure how to deal with the massive computational requirement tho...the fact that my training set would be like 3TB

I suppose I need to process on the fly

hmmm

but would that slow down the loading process like crazy...hmmm

or...train my own embeddings is option #3

prolly not

enumaris

21:28

hmmm....import matplotlib.pyplot as plt force closes my python

that's funky

that's funky tho, faulthandler flushes a traceback that flags a bunch of lines of code in the library...but it does not say what the actual error was...

user2723984

have you tried turning it off and on again?

enumaris

I upgraded it and it works now lol

DanielSank

22:26

@Blue Yes, that's mostly how science works.

bolbteppa

22:57

@Blue I don't see the Born rule in there :p

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