The h Bar

10:14 AM

Pop sci explanation of entanglement = bad

there is no "instantly"
The entangled pair is basically one object

when you measure it and it projected into one of the eigenstates, said eigenstate involve both A and B, thus if one is red, the other must be green (correlations)

It is not that the state is determined from the start except we don't know it
Rather it is the probability amplitude that is determined by the two systems interacting some time in the past

seriously old news

Secret

10:38 AM

How your gameplay helps ScienceAtHome build a quantum computer

►

This is why I think accurate visualisation is so important
Same equations, same problem, different presentation

One is formal and rigorous
Another is not as formal, but accurate enough and fun to play with

and when playing become research, it is win win

Perhaps we should write a program that simulate particle physics and QFT problems, and let the citizen scientist to solve it for us?

Slereah

11:04 AM

0

Q: quantum entanglement and its application in migratory birds

Explain the concept of quantum entanglement.Also explain its application in migratory birds. i know that it also has a relation with the magnetic field of the earth.

best question

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

go for it

i think i saw a ted talk on that once...

Physics Meta

1

Q: How can we encourage more Astrophysicists on SE?

I'm a relatively new user and have already noticed a lack of users with interest in Astrophysics, compared to Quantum Mechanics or Quantum Field Theory. I have interest in these more popular areas as well, so I am still enjoying the site, but it would be great to see more Astrophysicists on here!...

discussion

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

@0celo7 how could you even THINK that i would want you suspended? btw, you're not the first person to post a "star this if you hate me" message.

in Mathematics, Feb 16 '12 at 8:38, by Skullpatrol

To all those people who think Skullpatrol is annoying enough to be removed from this chat room: star this message (if the count is 3 or more I will not return) Thank you.

Slereah

11:54 AM

.Hm

How do you prove the Pauli Fierz identity without using any representation

$\sigma^\mu_{\alpha\dot\alpha}\sigma_{\mu\beta\dot\beta} = 2 \varepsilon_{\alpha\beta} \varepsilon_{\dot\alpha\dot\beta} $

ACuriousMind

@Slereah Um...It's a specific statement about the Pauli matrices in a chosen representation (the spinor one), is it not?

Slereah

Not quite sure

ACuriousMind

I'm pretty sure

Slereah

Though really it would be nice if there was a way to do it without doing it component by component

th.physik.uni-bonn.de/th/people/odakin/exerc/…

This bit claims it follows directly from the properties

Oh wait, maybe...

ACuriousMind

@Slereah Note that you can't even formulate the r.h.s. of the identity in a representation-independent way - at least I don't see how

Slereah

12:05 PM

$\sigma^\mu_{\alpha\dot\alpha}\sigma_{\mu\beta\dot\beta} \epsilon^{\alpha\beta} = \sigma^{\mu\beta}_{\dot\alpha}\sigma_{\mu\beta\dot\beta} = nI$

And on the other side...

ACuriousMind

(I must admit that I actually have no clue how the dotted/undotted notation works :D)

Slereah

$2 \varepsilon_{\alpha\beta}\varepsilon^{\alpha\beta}\varepsilon_{\dot\alpha\dot\be‌ta} = 4 \varepsilon_{\dot\alpha\dot\beta}$

fuark

I don't know

@ACuriousMind They are components in the spinor space

ACuriousMind

Well, duh :P

Slereah

There are four spaces

The basic spinor space

Dual spinor space

And then you can conjugate them

$\varepsilon$ is the metric of the spinor space

While $\sigma$ is a map from spinors to vectors

ACuriousMind

See, that's why I hate physicists' terminology. "Basic spinor space" is the space of right-handed Weyl spinors?

Slereah

12:08 PM

Hm

Been a while

ACuriousMind

Okay, let's start with the simplest thing: Is "basic spinor space" 2 or 4 dimensional?

Slereah

Let's check

IIRC it is $\Bbb C^2$, yes

And one is the left handed while the other is the right handed one

Well, not quite

I think it's something like $\psi_R = \psi_\alpha$ while $\psi_L = \psi^{\dot\alpha}$

ACuriousMind

That's horrible, I now remember why I never bothered to learn that notation :D

Slereah

yeah I think that's basically it

That way you get the correct $\psi_L^* \psi_R \in \Bbb R$

And the dagger maps upper to lower indices via $\varepsilon$

So more like $\psi_L^\dagger \psi_R = (\psi_{\dot\alpha})^* \varepsilon^{\alpha\beta} \psi_{\beta}$

At its core it's basically like differential geometry

there are just more vector spaces and complex numbers

yuggib

12:25 PM

you should all learn non-commutative integration and non-commutative probability theory...it's so fun ;-)

Slereah

is non-commutative integration the Grassman one

yuggib

especially you @0celo7... (I know you can't reply X-D)

@Slereah nope

it's more on this spirit

and non commutative probability is not so dissimilar

it's like doing standard integration and probability, but everything is automatically quantum

Slereah

Is that similar to like

errr

What's it called

The star thing

commutatertot

Moyal product?

Slereah

yeah

Phase space quantization

Emilio Pisanty

12:35 PM

Fun fact: as of January of this year, "(Color online)" is dead. At long last!

David Z

@EmilioPisanty really?

yuggib

@Slereah not really...that is a quantization thing

non-commutative integration/probability is already quantum

Slereah

Then I dunno m8

yuggib

I said that you all should learn it, not that you know it :-P

Emilio Pisanty

@DavidZ Yup. Go have a look.

Maybe start with this one

Slereah

12:38 PM

but I won't

Emilio Pisanty

journals.aps.org/pra/abstract/10.1103/PhysRevA.93.043408

Slereah

You nerd

yuggib

I suggest topics of interest to the community...

:-D

Danu

@EmilioPisanty What is this?

Emilio Pisanty

@Danu So all APS journals used to add "(Color online)" to the caption of every figure which was in colour in the online version but where the author didn't pay for colour prints online.

Which was about half the figures on pretty much every paper

Because, you know, journals.aps.org/authors/color-figures-print

> The charge is US $980 for a single color figure in print and $515 for each additional color figure in the print version of the article.

I found it really annoying

Much better the IOP way

Just say

> (Some figures may appear in colour only in the online journal)

upfront, and you're done

aaaand, finally, APS saw the light and dropped the tagline.

So: "(Color online)" is dead, long live color online!

=P

yuggib

12:49 PM

color figures...never a mathematician's problem (luckily)

btw, when you submit a paper with color figures you really pay the 980$ for each one that has to stay colored on the printed version?

do you have a special part of the fundings/grants/... dedicated to that?

Emilio Pisanty

@yuggib No, you pay $980 for the first one, and then $515 for each one after that

@yuggib That's the theory. I'm not sure who actually does that. Maybe papers from large consortia do it?

yuggib

@EmilioPisanty ok, nevertheless it is common to do that?

Emilio Pisanty

@yuggib No idea

yuggib

I assume you don't do that on your papers...

Emilio Pisanty

Best way is to grab a physical issue of phys rev whatever and skim for colour figures

Slereah

12:52 PM

"On Tuesday 4/3/12, I tweaked the "7 seals"/'beyond Einstein theories' that are revealed on the cover of the 74-page "book/scroll". The very minor revisions that I made was to better express the math equations in 'Seal #6'. I put parenthesis around (God=40/13mt) and moved it closer, so as to clearly make it a part of the 'Conglomeratal Energy eternal Theory'.

I also put parenthesis around '(gods e = 6m ui 10s 9t' and moved it closer, so as to clearly make it a part of the 'Conglomeratal Relationships eternal Theory'. "

Emilio Pisanty

No idea where I'd find one of those around here, to be honest

@yuggib Oh, no, no way. If people with a physical PRA issue (if there are indeed such people anymore) want to see my figures in paper, they can go download it and print it themselves. Latest paper would have cost $8,190 to print in colour, maybe a bit less.

You do have to make sure that your figures are readable on black and white though

mostly for people printing it at home on b/w printers

David Z

@EmilioPisanty a good point, often neglected. Which reminds me, I should check the paper I'm currently reviewing on that point.

I actually didn't realize (color online) was a standard thing. I've seen it, sure, but I read preprints often enough that I didn't see it often.

Emilio Pisanty

@DavidZ Yeah, this is not paid anywhere near enough attention.

Mostly, making sure your figures print reasonably in b/w also makes sure that they're legible to colorblind readers, and those probably make up something like 5% of your audience.

(assuming a male-dominated field and with a fairly broad definition of colorblindness)

@DavidZ Yeah, that's probably true in your field. Mine has something like 40% of papers making it to the arXiv, maybe?

I actually got told off by PRA editorial staff for not including it in my manuscript myself.

David Z

1:10 PM

@EmilioPisanty lol, can't say I ever had that happen.

I guess HEP is rather unique in having essentially 100% arXiv coverage

Emilio Pisanty

@DavidZ To that degree, yeah

Danu

@EmilioPisanty Ah...

Emilio Pisanty

@DavidZ Hmmm. Take that one with a grain of salt btw. I can't find that line now that I look for it.

David Z

Huh, well, not that it matters really. It's good that awareness of online PDFs is presumably high enough that the "(color online)" is no longer needed.

yuggib

@EmilioPisanty yeah, I guessed so

but maybe grants/fundings etc should take that point into account

and be adjusted to allow for color printing of published articles

I assume it is even a worse problem in other more figure rich sciences

Emilio Pisanty

1:21 PM

@yuggib Your budget is your budget, so unless it's earmarked for that specifically, you really need to consider whether your readers are better off with that or with you having better equipment to have better science to write about.

In that front there's similar stuff with open access APCs, e.g. the Wellcome Trust giving funds specifically for making papers open access.

That one is pretty important, but I don't think colour figures really qualifies, at least for a physics paper.

But say you've got some microscopy photographs with, say, structural information encoded in two different dyes? Then yeah, there's a stronger case for paying.

Not sure whether biology publishers tend to charge for colour or not, though.

David Z

Color ink is expensive, so I bet they would. Somebody has to pay for it.

I could see something like the Planck mission paying to have their papers printed in color, too. Astronomy in general has more need for color pictures.

Emilio Pisanty

@DavidZ Do they, though? Do we need colour figures in our print journals? Do we actually read the print version of journals enough for this to really matter? Is printing a bunch of figures in colour really the best use for research-directed tax dollars?

David Z

Well, I mean, assuming the figures are printed in color, somebody has to pay for it. I'm not saying they actually do need to be.

I know I personally don't ever read print versions, but I'm not discounting the possibility that a lot of people elsewhere do.

Slereah

1:44 PM

Hm

If I try to follow peskin or the symmetric lagrangian, I get different results

i wonder if they are identical in the end

Alex

@EmilioPisanty Thanks for the answer, very helpful.

Physics Meta

1:57 PM

0

Q: Posting a picture of my working

I am aware that stack exchange allows me to write beautifully typeset equations in LaTeX. What if, however, I am really lazy. Instead I write my problem out on paper and then take a picture and upload it? Will I get a whole load of moderators moaning at me? I often find that the amount of time ...

discussion

innisfree

2:16 PM

-1

Q: If a being was able to swallow itself, where would it go physically?

if a being was made from a special type of material that allowed it to stretch and was very flexible, if it were to swallow itself, where wold it go. I mean the physical aspects of it since it wont be here anymore. answer anyone?

kinematics universe projectile biophysics displacement

John Rennie

@innisfree words fail me

yuggib

the projectile tag is hilarious

also the universe one to a less extent

innisfree

Indeed. I laughed, then cried, then laughed again :D

John Rennie

@yuggib Projectile vomiting perhaps?

yuggib

@JohnRennie probably

Slereah

2:33 PM

Help

How did I get here

vzn

3:57 PM

@Secret "citizen science" is cool, and a trend, and hope it grows/ builds further, but its kind of a toy-level type concept right now. the "mass unwashed public" cannot contribute much more than gameplaying abilities or contributing distributed computing resources. so if one can do the heavy work to translate ones problem into those two (somewhat narrow) niches (agreed the qm moves game is well done! & apparently well funded!), its possible, otherwise, its still a near fantasy...

John Rennie

4:32 PM

Gosh it's quiet in here without 0celo7 and Barry Carter :-)

David Z

4:44 PM

Yep :-P

Slereah

Well find a topic

I dunno

skill patrol

why is there a dead link on Richard's profile?

Richard, UK

179k 36 1060 1353

star-wars star-trek story-identification harry-potter star-trek-tng movie star-trek-ds9

a whole year seems a bit harsh

John Rennie

If you mean the link to the chat room, that hat room has been deleted. I can still see it, but this presumably goes along with meeting some rep requirement.

skill patrol

@JohnRennie thanx for looking :-)

John Rennie

I don't know the details of what happened in the SFSE, but there was a big issue there with people behaving badly in the chat.

skill patrol

5:00 PM

ya, shog froze the room for a week

John Rennie

It's a bit surprising to see such a high rep user earn themselves such an extended ban, but tempers can flare up and people say things in the heat of the moment. We had a high rep used banned here under similar circumstances, though that was a while ago.

skill patrol

sophie?

John Rennie

Who is Sophie?

skill patrol

she used to be a regular in chat

John Rennie

Anyhow, I wasn't thinking of her. I'm not keen to name names, and in any case it was several years ago so ancient history now.

skill patrol

5:12 PM

as you said, the heat of the moment can be overwhelming for some

while some thrive on trying to light the fuse

DanielSank

6:18 PM

@JohnRennie Good grief the stars in that chat room say it all.

vzn

@DanielSank sounds like something "big" in the works. not many "places" have that kind of severe space constraint on content & would guess its "somewhere elite". are you writing up an experiment or something "else"? =D

you can signal stuff with english language to help it along like "consider the correspondence/ analogy with identical mathematical formalisms" etc

this reminds me of schroedingers eqn... maybe (for half fun, half edu) look at his historical paper for some ideas on how he set up/ introduced that tricky correspondence... although its probably in french right?

de broglie struggled with a similar issue also.

DanielSank

6:44 PM

@vzn Well we'll submit to PRL. Not sure if that counts as "big".

Slereah

Looking at AQFT

I'm thinking that maybe

I should learn algebra first

skill patrol

@DanielSank how many authors?

vzn

@DanielSank ok still topnotch; was guessing science or nature. oh well. maybe next time =D (your lab prob already has some, havent figured it out closely...)

← actually, 2nd thought, maybe PRL has more status/ impact among physicists anyway. science/ nature sometimes have problem of "jack of all trades, master of none..."

Slereah

"This algebra has the non-trivial center $Z = \{ A \in \mathfrak{A}, [A,B] = 0 \forall B \in \mathfrak{A}\}$"

Isn't... isn't that the definition of a center?

Oh apparently it's $\oplus_i \lambda_i 1_{\mathfrak{h}_i}$

Just a linear sum of the identities of the superselection sectors

(heheh, identitties)

vzn

@DanielSank oh & btw, for a physicist who almost likes english more than math, try reading some bohm (ha). wigner to shimony on bohms qm textbook: "too much schmooze"

Slereah

6:53 PM

Can't stop the smooze, @vzn

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