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00:00 - 21:0021:00 - 00:00

12:02 AM
Hi
 
@FenderLesPaul GR time?
 
I can't tonight I have an exam tomorrow :(
 
...
 
obe
12:23 AM
dw @0celo7 I will have GR time with you when I learn it in 3 months.
Also when I fix my damn mic for skype.
 
it's not the same
 
How's the tinnitus?
 
gone
thanks for asking
 
obe
12:42 AM
@0celo7 :(
 
12:55 AM
@obe you're gonna be at HE level in 3 months?
 
obe
Spinors and spacetime level dude.
 
ok, then you can explain chap 9 in Straumann which ACM was unable to
 
obe
I lied.
I'll be at wald level, is that ok?
 
Actually, I'm having trouble with a theorem that Wald omits and refers to HE
 
1:29 AM
hellooooo
 
helloooo
 
you should check my homework
 
what HW?
 
obe
Forebound seems like a word though it isn't a word.
 
@FenderLesPaul friction
I'm getting a really small number
 
1:35 AM
needs moar GR
 
found the error
nvm, you are not needed
 
obe
The reason my score is so high in the orbit game is because I used GR to place the astronomical objects instead of regular gravity.
 
you don't even know how to derive the geodesic equation
you probably don't even know what that is
 
obe
I do.
 
let's see
 
obe
1:37 AM
Later.
 
oh, when you have had time to read the wiki article
doubtful
 
obe
I am reputable here.
right.
well we will learn about the geodesic equation on the following week.
:(
 
and the truth comes out
 
obe
Wasn't it obvious?
 
@FenderLesPaul GR talk
 
1:44 AM
Friday :)
or Thursday :)
:O
:p
 
bish please I'm traveling
What exam am I being pushed aside for, anyway
@obe if you want help with the problem set, ask now
I've got some free time, I won't tomorrow
 
obe
I am doing my hs work.
Can you help out later this week please?
I'll begin soon.
 
I'm traveling from thursday to sunday
 
obe
It's due wednesday.
 
@0celo7 near east studies
 
2:00 AM
why are you taking that
 
general education requirement
 
yes but why that
 
oh
I like the subject it's pretty cool
and my friend was taking it too so I figured why not
in other news
finally finished my cover of A Team :D
 
2:39 AM
What's the difference in the Riemann tensor and the hessian in terms of the curvature information they measure? Is the riemann tensor contains curvature information at a point that is from the hessian already (that is is the curvature information from the hessian a subset of that in the riemann tensor?
 
Hessian tells you about extrinsic curvature of embedded submanifolds
 
@FenderLesPaul please make that more precise
I was just talking to an engineer buddy of mine about Hessians
 
idk why I changed it to extrinsic curvature
I meant Gaussian curvature
@0celo7 determinant of Hessian gives gaussian curvature of the surface
whereas its trace gives you the mean curvature
 
Hessian of?
 
the embedding map
 
2:47 AM
is that the function $f=0$?
 
gaussian is intrinsic, mean is extrinsic?
 
yeah
The gauss-codacci equations relate the two
 
yeah, I feel like I know this
I could read that section in Straumann
buuuuut, too tired
@PC gamers, Rockstar sale
 
Coming to chat to avoid posting a not-constructive comment that I'm just itching to issue.
4
Q: Can tin foil hats block anything?

StatusThis is joked about all the time, but... Can tin foil hats actually block anything? If they can, what frequencies? Is there any research into tin or aluminum foil and radio blocking or amplifying abilities when shaped into a hat? If they really don't do anything, what would be better? Radio blo...

Answer: Respectons. They block 100% of respectons.
 
2:56 AM
100% of womenons
 
obe
I think they're cool.
 
 
2 hours later…
5:16 AM
PDF Page 446 http://www.itp.phys.ethz.ch/research/qftstrings/archive/13HSStrings/StringsHS13Notes.pdf
"$[J_3,J^+] = J_3, [J_3,J^{-}] = - J_3$, In intuitive terms, this tells us the charges of $J^{\pm}$ with respect to the $U(1)$ subgroup generated by the Cartan $J_3$."
Huh?
What is this trying to say?
Also: "$|J^{\pm}>$ tranform with charges $\pm$ under the $U(1)$ generated by $J_3$."
 
6:03 AM
@0celo7 @ACuriousMind I remember asking you about the $1/2\pi i$ in the CFT charge $Q = \dfrac{1}{2\pi i}\int dz T(z) \varepsilon(z)$, think it's partially explained on page 55, section 7.5, here itp.phys.ethz.ch/research/qftstrings/archive/13HSStrings/… if you grok 7.46, point is there is an explanation, wahoo!
Needed that delta function to justify it as far as I can see
 
6:30 AM
Does anyone know any textbooks on phase space quantization (Moyal product etc.)?
 
@0celo7 if it's a woman wearing the tin foil hat, does it then block men?
 
Sigh
I think the most upvoted answer to that question should be edited to get rid of the jokey parts
 
I don't think so. IMO it's fine for an answer to have some humor as long as it does also constitute a proper answer.
 
 
2 hours later…
8:14 AM
@Danu There is a pedagogical introduction on chapters 22 and 23 of the book by Hall:
In the nlab page on geometric quantization there are many other refs...
 
8:28 AM
@Danu I have a paper about the link between phase space quantization and path integrals, if you want?
Hm, let's see
José Enrique Moyal, Quantum Mechanics as a Statistical Theory, Proceedings of the Cambridge Philosophical Society, vol. 45 (1949)
Aku Valtakoski, Mathematical Aspects of Functional Integration, University of Helsinki (2000)
also
 
@Slereah Oh, that's from Moyal himself? Neat.
@yuggib Thanks, I have this book
 
I think it's the original paper
basically you replace operators with regular functions but a weird multiplication
 
I'm currently at a conference about noncommutative geometry
It's all about this stuff :P
 
non-commutative geometry and physics or non-commutative geometry in general?
Alain Connes / van Suijlekoom stuff?
I would like to know better these things one day or another...not sure it is worth it though :P
 
In physics
There are also a lot of talks about nonassociative quantum mechanics
why.jpg
 
8:44 AM
I wonder if all formalisms of QM have a method to switch from one to the other directly
Or if in some cases you need intermediate steps
 
I would like to understand the "quantum mechanical" formulation of the Riemann conjecture given by Connes...but then I would have to know all about Adeles and so on o.O
 
@dmckee Democracy is sacred
 
George Washington died for your sins
 
 
1 hour later…
9:56 AM
"Freedom" is just another word for nothing left to lose...
 
 
2 hours later…
11:55 AM
0
Q: how about a what-if tag?

Carl WitthoftJust musing -- there are a measurable number of questions which, while more or less physics-related, are a much better fit for what-if.xkcd. Is it worth creating a "what-if" tag for these? The discussion at Are outlandish XKCD style What If questions welcome here? seems to suggest at least som...

 
12:22 PM
Good morning
Or whatever time it is in the third world
 
Hello
 
bonjour
 
@0celo7 'Morning' fits, I just woke up ;)
 
I know I'm getting better but these coughing fits are really annoying
@ACuriousMind so is there any hope of you reading page 212 ff in BBS and ELIE (explain like I'm an engineer)
 
12:39 PM
Hm
That question about pair production from graviton
Feynman had a student who did a thesis on electrons in covariant gravity
I think the answer should be in there
But I can't remember the name of it
Also it was awful
Typewriter thesis
Ah, the internet
 
My thesis is gonna be
 
Dissertation: Quantum mechanics of the interaction of gravity with electrons: theory of a spin-two field coupled to energy
That's the one
 
Multieyed Cyrillic demon letter thesis
 
As awful as I remember it
nothing about pair production though
p. 21 has it, though
 
@ACuriousMind read BBS...
Think of all the things I've done for you
 
12:56 PM
@0celo7 lol, I just looked at that. There's no way they develop the machinery to understand that in the hundred pages between where I stopped and where that is. :D
This book seems depressingly useless
 
They seem to just throw out random facts with very little motivation
Read the section on anomalies. Totally useless too IMO
Maybe not if you have more experience with anomalies in QFT
@ACuriousMind have you tried polchinski?
 
@0celo7 Not yet
 
1:18 PM
one of my professors, who is a string theorist, isn't very fond of BBS either
he says they just state things out of nowhere in passing with no justification
and you're left saying "what the hell?"
 
BBS.
?
Is that the Big Book of Strings
 
isn't that BBoS?
 
Becker$^2$ Schwartz
or something like that...
 
Indeed.
Apparently GSW is really good.
 
too many beckers
I only have one string book
It's the one like
introduction to the bosonic string
or something
I forget the author
 
1:32 PM
Is string theory an instrument?
 
booo
 
Is anyone on here a member of a professional physics society like APS or AAPT?
 
@Slereah sounds like polchinski
 
that's the one yeah
 
So someone posted a paper on the arXiv today that does exactly what I'm working on right now :(
 
1:38 PM
Sucks to be you
 
Exactly exactly?
Or can you expand on it
(PUBLISH OR PERISH)
 
@Sean I seem to recall @dmckee is
 
I can expand upon it yeah
they only did a holographic calculation
so I can just expand on the CFT calculation
it just sucks because the correlator in the CFT that I thought would characterize computational complexity of a black hole is exactly what they used too
but I scrapped the idea 3 months ago because for a 2D CFT with a local quench the CFT calculation became a bit too annoying to do :p
 
My laptop is dead. Physics lecture is gonna be so fuuuun
 
You're gonna have to actually listen and learn!
 
1:46 PM
I'm just wondering if it's actually worth while to join one
 
Do they charge dues?
I wouldn't think so unless you're doing research and need the connections
 
oh yeah, and they aren't cheap
I thought particularly that AAPT might be good, because i'm a physics teacher
 
I'm the only resource you need to be a better teacher
 
plus it would be nice to have access to the journals, since it's not like i'm tied to a university that has access
 
I can tell you what to do
Rule 1: it's never too early to introduce tangent bundles
 
1:51 PM
but I know with APS, the journals are still $50 bucks per online subscription even with a membership
yeah, i don't know what a tangent bundle is
ostensibly related to a fiber bundle
 
Rule 2: it's never too early to tell them that electrons are 511keV photons in a Dirac's belt configuration
 
@0celo7 : Introduce it when you do Newton's law
 
Rule 3: quantum fluctuations are real
 
None of that "vector in R^3" business
 
Exactly.
If you're not learning mechanics from Arnold you're doing it wrong.
 
1:53 PM
hahaha yeah i teach real physics. none of this "electrons are light" business
@ACuriousMind gets so pissed at the phrase "quantum fluctuations"
 
Another popsci cargo cult intellectual garbage man denying bona fide physics, Einstein and the Evidence
 
@0celo7 Well...$\langle A^2 \rangle - \langle A \rangle^2$ is real, that's correct...
 
quantum fluctuations are responsible for Donald Trump's success
 
anyway, i just didn't know if joining APS was something that everyone whos anyone did, or if it was more restricted to people doing major research who are publishing
 
@FenderLesPaul people who drag politics into chat deserve death >:(
@ACuriousMind no, I mean in space there are virtual particles popping in and out of existence
 
2:00 PM
Not taking the bait :P
 
There's no bait, Zee says that
Are you telling me a physicist would just lie
@Sean can only physicists join?
 
@Sean probably many of us are APS or equivalent members
 
Nuclear engineers can end up doing physicsy things
 
@0celo7 No you fool
Think of Einstein and the evidence
 
@Sean no, there are no restrictions. Anyone can join. Only a fraction of the membership (30% maybe?) are research physicists.
 
2:04 PM
On mobile, no clue what statement makes me a fool
Is evidence the same thing as The Evidence?
 
2:16 PM
@DavidZ do you feel like it's worth the dues for a high school physics teacher?
I'd like to do AAPT for sure, but i didn't know if APS would also be valuable
 
eh, not really. Actually even for researchers, the only reason I think APS is worth it is that if you're not an APS member everyone else in the community will wonder what's wrong with you ;-)
(this is for Americans, of course, not foreigners)
 
I think ACM should become a high school physics teacher.
 
That being said, the APS meetings do often have some interesting presentations on education research, which might make it worthwhile for you. And I think (though not sure) you get a substantial discount on meeting fees for being a member.
 
do you go to a lot of the meetings?
I know @DanielSank has said that he goes to some
 
2:32 PM
really saying that virtual particles aren't real is fine, but then you have to remember that real particles aren't either :p
 
What did Einstein have to say on the matter?
 
not sure
How old is the notion of virtual particle
40's?
 
No clue.
One can only hope Bajoran writes a QFT saga and sets us all straight on the matter.
 
3:14 PM
Hi guys, I am your old Godparticle (now Feynman), can you all support me in this proposal of creating polymath.stackexchange community:
 
God, now I have a runny nose. I feel like a 5 year old 😩
 
10
Q: What are the funerary rites of Gnoll worshipers of Erythnul?

The GuardianI'm playing a Gnoll Cleric who worships Erythnul in a D&D 3.5e game. Sadly one of my party members died in our last session (he's not a Gnoll). I would like to do something with his body (not just leave it where it fell). What are the funerary rites of an Erythnulian Gnoll? As a lore question, ...

Role-playing Games is great. :D
 
Nerrrrrrd
 
Yes :)
 
3:30 PM
@ACuriousMind: Can you support my proposal?
See above..
 
@Feynman I don't see a need for it. What kind of questions could you ask there that you cannot ask on any of the individual science sites? There are no example questions or definitions of scope yet.
 
Okay, I am editing the questions now.. One of the example would be physics.stackexchange.com/questions/201530/…
that connects...
math, physics, history..
that is polymathic...
@ACuriousMind: I hope you are here...
I hope to see the site to be a home of questions which used to cross-posted...
@ACuriousMind: Can you support me now?
 
@Feynman But...that question is on topic here, and possibly also at History of Science and Mathematics
Why do you want a site that would only siphon questions away from other sites?
 
Polymathic questions need attention of all the experts not just an physics, or math or history expert, so I see the requirement...
Can you support me now? :)
 
3:49 PM
No, because I do not see the need for such a site. Almost all questions which actually "need" an expert in multiple fields are too broad for the SE model, anyway.
 
Okay...
@ACuriousMind: But, don't you think polymathic questions to be not broad for a polymath?
Can you support me now? :)
 
"Too broad" is not a characterization that depends on the answerer. It means a good answer is necessarily almost a book, since it needs to take so many things into account. If it doesn't need to, then the question could as well be answered on one of the existing science sites.
Also, I don't think "polymaths" still exist, we have accumulated far too much knowledge for that
What exists is people knowing things from more than one subject, but that's far from being a polymath, i.e. an actual scholar of multiple subjects.
 
@Sean sorry, missed that - I've been to three of them
They tend not to be particularly important
at least, not compared to specialist conferences
 
4:12 PM
Sorry, I see faults in your reasoning, don't you think good answer to be not necessarily a book, if the answerer is really a polymath (atleast who is trying to become a polymath)? Atleast answer to the question which linked need not need a book...
My aim is to have community who wants to become polymath...
It is a motivation...
 
@ACuriousMind Kerbal Space Program?
 
Add the letter "I" In between "which" and "linked" in my previous comment..
 
@0celo7 That's not a question ;)
 
Okay, I am leaving...
 
@Feynman bye
Finally got GTA4 to work properly.
@ACuriousMind See the question mark? Do you even English?
 
4:59 PM
@0celo7 Yeah, but...what do you want to ask? "Why do you play it?" "Is it good?" "What is it?" Something else?
 
@ACuriousMind Yes, read my mind (I knew you would).
 
@0celo7 I did not ask a Yes/No question, what kind of answer is that?
 
5:14 PM
Do you stop getting rep points for edits after 2k rep?
 
@Sean Yes.
@ACuriousMind One that makes you think.
(All of the above)
 
that's no fun
i guess now i just keep editing out of altruism
 
@Feynman I'd be worried people would confuse polymath for things like the Terry Tao polymath projects.
@Feynman and I really don't think that question is a polymath question... it's exactly what HSM is for I think. The kind of people who read Newton oand related with a modern eye.
I could be wrong about that last bit as I'm not involved in the site at all.
 
6:09 PM
@NeuroFuzzy: Sorry, the question I asked was more alligned towards math, but it does require expertise in math and history along with some physical intuition. We can find many questions which require knowledge of different fields of science...
Have a look at this
0
Q: Connecting different sites

FeynmanProposal: Polymath I have seen questions being cross-posted. I want to make a site for those type of questions which requires polymathic folks. If the questions posted in poymath site is tagged with different subjects (and SE exists for that subject), say physics, math and history; we can progra...

@ACuriousMind: Have a look at the above question..
@0celo7: You may also look at the question, and I will be glad if you support my proposal..
 
@ACuriousMind In the plane, are all closed forms exact?
 
6:47 PM
@0celo7 : Zero-forms are never exact but could be closed.
 
@Qmechanic I meant one-forms.
Because in differential equations, we have exact equations, but the method for checking that they are exact is really just computing the exterior derivative...
So really we're just checking that they're closed...
 
7:13 PM
@0celo7 You should know that. :P Which object tells you whether closed-but-not-exact forms exist?
 
"You can observe a lot by watching."
"Nobody goes there anymore. It's too crowded."
"Always go to other people's funerals, otherwise they won't go to yours."
Lawrence Peter "Yogi" Berra (May 12, 1925 – September 22, 2015) was an American professional baseball catcher, manager, and coach who played 19 seasons in Major League Baseball (MLB) (1946–63, 1965), all but the last for the New York Yankees. An 18-time All-Star and 10-time World Series champion as a player, Berra had a career batting average of .285, while compiling 358 home runs and 1,430 runs batted in. He is one of only four players to win the American League Most Valuable Player Award three times. Widely regarded as one of the greatest catchers in baseball history, he was elected to the Baseball...
 
user54412
@ACuriousMind Is it good? I've heard it's fun, but I've also heard it really fakes the dynamics in a number of ways.
 
7:29 PM
@ACuriousMind ::mumbles something about co/homology::
 
7:51 PM
@ACuriousMind D: I've forgotten what exactly I need
 
@0celo7 It's the cohomology - since deRham cohomology is precisely the closed modulo the exact forms. All closed k-forms are exact if and only if the k-th cohomology vanishes.
 
I knew that
 
@ChrisWhite Well...given the weird contraptions I've brought into flight, I'd guess at least the aerodynamics are not that realistic...but realistic enough that I've killed about three dozen kerbonauts trying to get one into a stable orbit :P
 
I've forgotten how to calculate it D:
 
@ChrisWhite So, I think it's very fun, but you'll probably find lots of small things to complain about if you know a lot about aerodynamics and orbital dynamics.
@0celo7 Hint: The plane (any $\mathbb{R}^n$ really) is contracible.
 
7:58 PM
Guys, I have edited the description of the proposal..
See here..
1
Polymath

Proposed Q&A site for polymathic community. The site covers CRITICAL questions which can be answered only by a partially or completely polymath field expert, and which may not be answerable by a unique/non-polymath field expert.

Currently in definition.

Do follow, if you are interested...
Must follow if you are a polymath :)
 
@ACuriousMind like "I have no clue where to start" forgot
@ACuriousMind Do I use the de-Rham theorem and then calculate the homology?
And is there something about the homology of contractible spaces?
 
8:16 PM
@0celo7 : LOL, you got it kid. Right after the pair production and the electron diffraction and the annihilation.
 
@Feynman That's not going to fly. I'm genuinely surprised that you got this far.
 
@0celo7 Why do you want to use something about the homology? Use something about their cohomology! (Namely, unpack what "contractible" means, and then use that (co)homology is homotopy invariant)
Then all you need to know is the (co)homology of a point.
 
@GlenTheUdderboat: I didn't get you..
 
@Feynman No worries. Good luck!
 
@ACuriousMind well I don't know that either D:
for shame
how do you even have 1-forms on a point
D:
 
8:30 PM
@GlenTheUdderboat: Thank you!!!
 
if I have rope over multiple pulleys (assuming a perfect rope and ignoring the mass of the pulleys), is the tension in the rope the same along each free part?
 
@0celo7 Ignoring gravity, I'd say yes. Assuming that "free" means between pulleys.
 
@GlenTheUdderboat yes, that's what I mean
why ignoring gravity
that's just another force on the stuff the pulleys are connecting
 
@0celo7 You...don't.
 
@ACuriousMind what do I do then!!?
 
8:37 PM
@0celo7 Well, in general, for pulleys it matters whether they are fixed or not. And if you're going to ignore mass, why not ignore gravity?
 
@0celo7 Well, there aren't any forms except 0-forms on a point. So its deRham cohomology vanishes in all but the zeroth degree, no?
 
@GlenTheUdderboat you don't ignore gravity on the masses connected by the ropes
@ACuriousMind ffs
 
@0celo7 OK
 
so that works in all R^n?
 
@0celo7 Still yes.
 
8:39 PM
well now I'm confused
 
@0celo7 Yes. All $\mathbb{R}^n$ have vanishing cohomology except for the zeroth degree, where it is $\mathrm{R}$ (or $\mathbb{Z}$ or whatever you're computing the coefficients in).
 
ok, what about that one vector calc thing $\nabla\cdot B=0$
so we can have $B=\nabla\times A$ globally?
or am I just confusing things
what is happening
 
The (co)homology of the pulleys determines the invariant tension of the massless rope.
 
or is it curl grad f =0 that I'm thinking of
@ACuriousMind halp
@GlenTheUdderboat D:
this was not discussed in class
the acceleration of A is going to be twice that of B, right?
I'm going nuts today
 
@0celo7 The distance travelled is. So why not the acceleration (being the second derivative)?
 
8:49 PM
@GlenTheUdderboat that's exactly how I made that determination...just checking
 
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