The h Bar

Sir Cumference

19:24

@Secret Huh, you managed to keep in touch? What's your Secret?

Secret

19:42

We are part of the generation before social media (probably the last of the non social media generation before it rises), and we occassioanlly make phone calls to each other. In the age of social media, we evolve with it. But most importantly, every 1-3 years, we met face to face, known as gatherings

Sir Cumference

@Secret Dang, I should do that now before I really get out of touch with them

@DavidZ Hmm...what do you think of this favicon?

Tell me if you have any other ideas besides the moon

Wait, I just had an idea...

I could have the moon's phase change on the favicon depending on the real life phase of the moon

Secret

20:07

Another day of bad sleep due to extremely hot weather in Syd.

Secret

20:32

Quantum optical sensor now in space. Preparing to test the equivalence principle

Exploring Jupiter's deep jets in a lab model

Axion photon coupling is equal in a toroidal magnet as in a solenoid, providing groundwork for new axion detectors

Frame the message in align with their worldviews to get them to listen. Also the more curious people tend to be more open minded

Maks

@SirCumference why the moon?

Sir Cumference

@Maks Cause it's in space

Maks

20:47

Well earth is in space too

Why didnt you put the earth ? :D

Sir Cumference

That's better for earth science :P

Maks

Do a voting on what favicon should it have (?

Damn that grammar

What happened with the barbecue ?

Secret

(Old news) Meanwhile I have an opposite problem: I rely too much on the maths to derive the physics and thus lost track of the phsical reality

Sir Cumference

It's so hard to find public domain things I can use

Maks

You can design one

what do you want to do ?

user223506

21:19

heh - random downvote here and on SO at almost the same time - someone had a tantrum with me...lol

ACuriousMind

Help! @Slereah you've looked into Rarita-Schwinger stuff, right? Please write down the correct covariant derivative of an R-S spinor (and hopefully convince me I'm not going mad).

Slereah

Whaaat

I mean I have it somewhere

But beware

There are several versions to write it down

ACuriousMind

I...think I can tell those compatible with my understanding from those incompatible with my understanding

My problem is that the papers seem to say that the vector index on the gravitino needs no Christoffel

user223506

who would have though that static electricity would cause so much angst

Slereah

One version I've seen is $$(((\gamma^\rho \partial_\rho) \delta^\mu_\nu - (\gamma^\mu \partial_\nu + \gamma_\nu \partial_\mu) + (\gamma^\mu \gamma^\rho \partial_\rho \gamma_\nu)) - m(\delta^\mu_\nu - z \gamma^\mu \gamma_\nu)) \psi^\nu$$

With $z$ some free parameter

ACuriousMind

21:27

what on earth is that

Slereah

Well for short it is just $$[D^\mu_\nu - m\Theta^\mu_\nu] \psi^\nu$$

ACuriousMind

Aha, alright. If $m$ is the mass of the R-S field we can set it to 0 for now. What is $D^\mu_\nu$?

The usual covariant derivative operator has just one index, no?

Slereah

It's the lorentz invariant derivative

Well it's the equivalent of $\gamma^\mu \partial_\mu$

except fancier

ACuriousMind

You see, the funny thing is that all these supergravity papers just write $D_\mu \psi_\nu = \partial_\mu \psi_\nu + \frac{1}{4}\omega_{\mu ab}\Gamma^{ab} \psi_\nu$ and call that the "covariant derivative".

Balarka Sen

it occurs to me that one could potentially make a good slasher movie out of the indices from a GR book

ACuriousMind

21:31

I.e. they just write down the cov. derivative of the 1/2-spinor part and seem to completely ignore the vector index

Slereah

Maybe it's one of those fancy DeWitt index

user223506

one of the funnier exchanges I witnessed - 2 members having a comment stoush around my answer (I did not engage) because one wanted me to add in irrelevant 'pet' information (I didn't) - end result, one member deletes all his comments, possibly downvotes me, writes an answer with the irrelevant information and gets downvoted (not by me)

Slereah

Where $\mu$ represents like 5 indexes

ACuriousMind

(here, $\omega$ is the spin connection and $\Gamma^{\mu_1\dots\mu_p}$ the antisymmetrized product of $\Gamma$-matrices)

Slereah

Another version, if you wish

there's also the original version by Wigner somewhere

ACuriousMind

21:33

Ahhhh

I think I know what my problem is

user223506

omg I am invisible starts undressing

ACuriousMind

Their "covariant derivative" is such that the kinetic term reads $\psi_\mu \Gamma^{\mu\nu\rho} D_\nu \psi_\rho$. And the terms that would spoil invariance due to the vector index are symmetric in $\nu\rho$, so they don't matter.

Thanks, @Slereah, it appears I just needed to ramble a bit

Slereah

np

heather

@Doc eesh =)

ACuriousMind

@Doc Wait until they begin posting answers/questions just saying what a psychopath you are, that's when the real fun begins

We had a rather persistent troll like that a while back

user223506

21:41

@heather all over static electricity of all things - physics.stackexchange.com/a/307010/140434

user223506

@ACuriousMind I'd probably enjoy that

user223506

@ACuriousMind who did they target?

Secret

22:11

Why is the chat so dead during the periods I am awake ::So few australians... ::

user223506

ahem

user223506

<-- Western Australia

Secret

well, still few

you and wendy pretty much

heather

i'm around, and i'm not in australia

it's mid/late afternoon for me

Secret

It's morning here

user223506

22:20

I am trying to think how to word a question....

Secret

In other news, I think I need to figure out why in a SE chat room I create, the feeds does not seemed to be working

user223506

if I were to post my question as it currently stands, it'll probably be downvoted and I'd get the 'writing-advice-commentary'

user223506

and no answer, and no ice cream

ACuriousMind

@Secret That's because you didn't add the correct feeds.

In order to get to the feed for a tag, hover over the tag, then click the "rss" in the upper right corner of the card that pops up.

AccidentalFourierTransform

that "Einstien" in the stardboard is gonna make my head explode

David Z

22:33

@SirCumference That could work

@SirCumference Just look at NASA, they publish a ton of public domain stuff

user223506

gah!

heather

@AccidentalFourierTransform you just ruined the starboard for me ::groans in agony::

AccidentalFourierTransform

lol

user223506

I keep on re-drafting my question...

user223506

dang it...

Secret

22:47

Acuriousmind: O cool, the feeds are working now

heather

hmm, i thought of an interesting problem the other night and i can't seem to figure out a general way to find a solution.

(if anyone is interested i would be glad to share it)

user223506

screw it, deleting the question draft - I'll figure it out

ACuriousMind

@heather How am I supposed to tell whether I'm interested in the problem before you've told us what it is? :P

Kenshin

Hello

heather

@ACuriousMind lol, fair enough. i was climbing and someone mentioned a challenge: climb using only the "wrong side" of the holds. then, i started thinking: what shape would not have a "wrong side" (i.e., all sides are equally poor to hold onto).

user223506

22:57

@heather similar - tried to write it as a question

ACuriousMind

@heather ...a rotationally symmetric shape?

Emilio Pisanty

booya! 600 rep in three days!

user223506

woah!

Emilio Pisanty

you can definitely tell term just started

user223506

i'd be lucky to get 600 rep in say, a year

Emilio Pisanty

23:01

@Doc most of this catch is from multi-year-old homeworky posts

well, not homework, but dancing around concepts that an undergrad would ask

user223506

@EmilioPisanty ah!

user223506

I answer those type of questions

user223506

wait a sec - I do have 600 rep! (not including the assoc bonus)

user223506

but that took me 27 days

user223506

10 answers

Emilio Pisanty

23:04

@Doc If there aren't enough good questions in your area, write some!

user223506

@EmilioPisanty I tried drafting a question.... but I can't seem to word it, so it A) makes sense and B) doesn't sound homeworky (because it is not)

ACuriousMind

@EmilioPisanty You hit the rep cap from old questions alone? oO

Emilio Pisanty

@ACuriousMind not quite, but it goes a huge bit of the way there

user223506

at my rate - I should hit 1k by sometime in the early to mid 22nd century and 10k by the time the sun turns into a red giant

user223506

I have given up on SO

Emilio Pisanty

23:08

@Doc SO is a tough place

@Doc and it is not about the rep

it's about writing good content

user223506

@EmilioPisanty I have 3 questions and 13 answers.... with a pretty crappy track record

user223506

I try to write good content

Emilio Pisanty

@Doc so practice some more

user223506

@EmilioPisanty I have redrafted a question that i want to ask several times

user223506

and looked over well received questions here for guidance

heather

23:11

@ACuriousMind hmm, but that's not quite it

well, i guess...

hmm.

AccidentalFourierTransform

it turns out that Zinn-Justin's book on QFT is exactly what I was looking for

it has a chapter that is 10/10

user223506

I just don't think my question is good enough

Emilio Pisanty

@Doc just don't let perfect be the enemy of good

ACuriousMind

@AccidentalFourierTransform Regarding what?

user223506

the worst case scenario for a question is not the downvotes, but the comments regarding writing style etc

AccidentalFourierTransform

23:14

18

Q: Functional differential equation (from Quantum Field Theory).

I have a certain differential equation that includes functional derivatives. I know the solution, but I'm having a hard time to show that the equation is indeed solved by the solution. The background for this question is quantum field theory (in particular, scalar $\phi^4$). The equation, called...

@ACuriousMind I asked that ^ some thime ago

the chapter addresses that and so much more

user223506

'nitpicking' the question would be the worst response to a question and what I am trying to avoid

AccidentalFourierTransform

me likey

ACuriousMind

@AccidentalFourierTransform 500 rep bounty! That's the sign of true dedication or an approaching deadline.

Secret

An illustration of multiverses

AccidentalFourierTransform

@ACuriousMind I offered up to 100 rep points in math.SE before

and I got no answers/comments

nothing

there are always like >60 questions in the bounty tab

you have to offer a lot or people just ignore the question

user223506

23:17

hmmmm - my answer here physics.stackexchange.com/a/302645/140434 will be deleted, as the question is closed, won't it?

ACuriousMind

@Doc No, questions of positive score or questions with positively scored answers will never be deleted.

(at least not automatically, and I see no reason to do it manually here)

@AccidentalFourierTransform Ah, yes, I forget how large math.SE is sometimes

user223506

@ACuriousMind really? But no doubt, members will vote to delete it?

ACuriousMind

@Doc Why would they?

I sse nothing about the question or the answer that warrants deletion. There's no policy that off-topic questions must be deleted (in fact, that would hinder the possibility of editing/reopening them).

user223506

@ACuriousMind same reason as the close reason?

AccidentalFourierTransform

Jan 4 at 12:41, by AccidentalFourierTransform

@Doc If the question is closed but it already has an answer it wont get deleted

@Doc you asked that here before =P

as I told you the last time: no, the question won't get deleted

user223506

23:25

okay... still a bit 'nervous'

AccidentalFourierTransform

something something fake internet points amirite?

user223506

um no

user223506

@AccidentalFourierTransform no, that is not it

user223506

my 'nervousness' (for want of a better term) is borne out of concern about wasted effort

AccidentalFourierTransform

all effort is wasted

welcome to the real life

user223506

23:34

anyway, got to go... have to walk (or in my case, limp) the 4km to work (speaking of real life wasted effort)

user223506

point taken

AccidentalFourierTransform

see you around :-)

user223506

@AccidentalFourierTransform not likely

AccidentalFourierTransform

what?!

why? you aint coming back?

...

kbye

Secret

After so much procrastination, finally returning to solve this problem: Show that a mass dipole under any configuration cannot be used as a perpetual motion generator

Man, rotational mechanics is so messy...

GPhys

23:48

What do you guys think about L&L's two E&M books for graduate E&M course material?

(US)

that's the text we're using four our class (I'd expected we would be using Jackson)

but I'm contemplating picking up Jackson to supplement the material (?)

Transcript for